What is your minimum order quantity?

For a part made to your drawing or sample, the minimum is usually 100 pieces per item. For a standard size, put the quantity you need on the request and we confirm it in the quotation.

How long does production take?

A non-standard part usually takes 25–30 days to produce. Standard sizes in stock usually ship in about 3 days for a small order and about 7 days for a bulk order. The dates for your order are confirmed in its quotation.

Do you publish prices?

No. The price depends on the size, grade, length and quantity, so send those on the quote form and we quote the part.

Which sizes do you keep in stock?

18 protection tube sizes, 15 insulator sizes and 12 furnace tube sizes are usually in stock. Each size page says whether that size is usually in stock or made to order.

Which sizes are made to order?

Another 18 insulator sizes on our list are made to order rather than held in stock, and so is any size made to your drawing. Request them like any other size, and the quantity and date are confirmed in the quotation.

Is my tube length in stock?

Stock sizes are cut to the length you order, so put the overall length on the request. Our protection tubes have been made from 300 to 2500 mm long, and the protection tube sizes guide lists the standard lengths.

Can you make a part to our drawing or sample?

Yes. We make parts to a drawing or a sample by slip casting, pressing, extrusion or hot pressing: tubes, rods, crucibles, boats and special shapes. See custom components.

What is the largest tube you can make?

Extruded tubes up to 17×10 mm (OD × ID) and slip-cast tubes up to 100×90×1000 mm (OD × ID × length). Large furnace tubes are in stock: OD 80, 75, 70, 65 and 60 mm at 1–1.2 m; OD 50, 45 and 35 mm at 1.5 m; OD 40 and 30 mm at 2 m. See furnace tubes.

What should the drawing or request show?

OD, ID and length with tolerances, the Al₂O₃ grade, the ends, the quantity, and any insert or wire that has to pass through. The tolerance guide shows how to write them. PDF, DWG, DXF, STEP, IGES, PNG and JPG files all work.

What tolerances can you hold?

On closed-end protection tubes we quote ±0.5 mm on OD and ID for OD 6–12 mm, ±0.6 mm for OD 15–17 mm, ±0.7 mm for OD 20 mm and ±1.0 mm for OD 24 mm, with ±1 mm on length and straightness to 0.1% of length. Tolerances are agreed per order. On the tubes we supplied in 2026, buyers' orders called for ±1 mm on length and from ±0.35 mm on a 6 mm OD to ±1 mm on a 24 mm OD. The full table is in our alumina tube tolerances guide.

Can you make the ID one-sided?

Yes. If the bore matters more than the nominal size, we can make the ID one-sided, for example 10 +1/−0 so it is never under 10 mm, and we write the insert test on the order.

Will our insert reach the bottom of the tube?

We test-fit tubes before dispatch. On a 15×10 closed-end tube, an 8.5 mm core reaches the bottom and a 9.5 mm rod doesn't. Name the insert or core that has to go in on your order.

Which tubes fit together as a double protection tube?

Our standard pairings are a 12×8 tube inside a 20×15 tube, and a 10×7 tube inside a 17×13 tube.

Can we get samples before ordering?

Yes. We usually send 5–10 samples for you to approve before the order runs. Ask for them on the quote form with the size and grade you want to test.

Yes. Samples are free and are usually short pieces of the size you want. You pay the courier freight. If you need to test a longer piece, 500 mm and 1000 mm sample lengths both work.

What alumina grades do you make?

Our standard grade is C799 alumina, 99.5% Al₂O₃. We also make 95% white alumina, which we supply where a drawing names C 610. We confirm the grade and maximum temperature for each part in its quotation, and our grades are compared here.

What is the maximum temperature of your tubes and crucibles?

In air, our corundum tubes are used up to 1,750 °C hanging vertically and 1,650 °C lying horizontally, and our crucibles up to 1,650 °C. Vacuum, load, fast heating and alkali vapour bring the limit down, as the alumina maximum temperature guide explains.

Our drawing says C 610. What do you supply?

We supply 95% white alumina or our standard C799 alumina instead. Neither is mullite; the grades guide shows which suits your thermocouple and atmosphere.

Do you make zirconia or porcelain crucibles, or combustion boats?

We make alumina: crucibles, boats and lids in alumina, used up to 1,650 °C in air. We don't make zirconia or porcelain crucibles, or combustion boats and tubes for carbon-sulfur analyzers. When alumina is the right choice is in porcelain or alumina crucible and alumina or zirconia crucible.

Are you ISO 9001 certified?

Yes, for protection tubes. Our ISO 9001:2015 certificate, registration 06525Q02034R1S from CFL Certification Center, covers the manufacturing of ceramic protective tubes for thermocouples and is valid to 5 August 2028. The certificate is on our quality page.

Do you have a lab test report or certificate of analysis?

An independent lab, Chinalco Testing Technology (Zhengzhou), analyses one of our alumina tubes every year: 99.55%, 99.57% and 99.61% Al₂O₃ in 2024, 2025 and 2026. The 2026 report is on our quality page, and the earlier reports are available on request.

How do you inspect the tubes?

Outside and inside diameters are checked with 0.02 mm vernier calipers. Put the tolerances that matter on your drawing and we confirm them in the quotation.

How are parts packed for export?

Tubes are bubble-wrapped or bundled in stretch film, with foam end-blocks and foam sheets between layers, in foam-lined plywood crates that are strapped and stacked on pallets. Small insulators go in 1 kg bags inside foam-lined wooden boxes, and crucibles sit one per cell in a foam grid. We confirm packing and marking for each order.

Where do the parts ship from?

They're made and packed at our factory in Tangshan, Hebei, China. Put your destination country and the Incoterm you want on the request.

Are you a factory or a trading company?

A factory. GY Alumina is the export brand of Tangshan High Aluminum Corundum Industrial Ceramics Factory (唐山市高铝刚玉工业陶瓷厂) in Hebei, and the parts on this site are made there. See the factory.

How do I request a quote?

Use the quote form or email sales@gyalumina.com with the size, grade, length and quantity, plus a drawing if you have one. We reply within one working day.

Buyer FAQ: MOQ, Lead Time, Samples, ISO 9001

Standard sizes usually ship from stock in about 3–7 days. Parts made to your drawing usually start at 100 pieces per item and take 25–30 days to produce, with 5–10 free samples sent for your approval first (you pay the courier). Our ISO 9001:2015 certificate covers protection tubes, and an independent lab analyses one of our alumina tubes every year (99.61% Al₂O₃ in 2026). Send the size, grade and quantity and we reply within one working day.

Minimum order and lead time

What is your minimum order quantity?: For a part made to your drawing or sample, the minimum is usually 100 pieces per item. For a standard size, put the quantity you need on the request and we confirm it in the quotation.
How long does production take?: A non-standard part usually takes 25–30 days to produce. Standard sizes in stock usually ship in about 3 days for a small order and about 7 days for a bulk order. The dates for your order are confirmed in its quotation.
Do you publish prices?: No. The price depends on the size, grade, length and quantity, so send those on the quote form and we quote the part.

Stock or made to order

Which sizes do you keep in stock?: 18 protection tube sizes, 15 insulator sizes and 12 furnace tube sizes are usually in stock. Each size page says whether that size is usually in stock or made to order.
Which sizes are made to order?: Another 18 insulator sizes on our list are made to order rather than held in stock, and so is any size made to your drawing. Request them like any other size, and the quantity and date are confirmed in the quotation.
Is my tube length in stock?: Stock sizes are cut to the length you order, so put the overall length on the request. Our protection tubes have been made from 300 to 2500 mm long, and the protection tube sizes guide lists the standard lengths.

Custom sizes and drawings

Can you make a part to our drawing or sample?: Yes. We make parts to a drawing or a sample by slip casting, pressing, extrusion or hot pressing: tubes, rods, crucibles, boats and special shapes. See custom components.
What is the largest tube you can make?: Extruded tubes up to 17×10 mm (OD × ID) and slip-cast tubes up to 100×90×1000 mm (OD × ID × length). Large furnace tubes are in stock: OD 80, 75, 70, 65 and 60 mm at 1–1.2 m; OD 50, 45 and 35 mm at 1.5 m; OD 40 and 30 mm at 2 m. See furnace tubes.
What should the drawing or request show?: OD, ID and length with tolerances, the Al₂O₃ grade, the ends, the quantity, and any insert or wire that has to pass through. The tolerance guide shows how to write them. PDF, DWG, DXF, STEP, IGES, PNG and JPG files all work.
What tolerances can you hold?: On closed-end protection tubes we quote ±0.5 mm on OD and ID for OD 6–12 mm, ±0.6 mm for OD 15–17 mm, ±0.7 mm for OD 20 mm and ±1.0 mm for OD 24 mm, with ±1 mm on length and straightness to 0.1% of length. Tolerances are agreed per order. On the tubes we supplied in 2026, buyers' orders called for ±1 mm on length and from ±0.35 mm on a 6 mm OD to ±1 mm on a 24 mm OD. The full table is in our alumina tube tolerances guide.
Can you make the ID one-sided?: Yes. If the bore matters more than the nominal size, we can make the ID one-sided, for example 10 +1/−0 so it is never under 10 mm, and we write the insert test on the order.

Insert fit and double tubes

Will our insert reach the bottom of the tube?: We test-fit tubes before dispatch. On a 15×10 closed-end tube, an 8.5 mm core reaches the bottom and a 9.5 mm rod doesn't. Name the insert or core that has to go in on your order.
Which tubes fit together as a double protection tube?: Our standard pairings are a 12×8 tube inside a 20×15 tube, and a 10×7 tube inside a 17×13 tube.

Samples

Can we get samples before ordering?: Yes. We usually send 5–10 samples for you to approve before the order runs. Ask for them on the quote form with the size and grade you want to test.
Are samples free?: Yes. Samples are free and are usually short pieces of the size you want. You pay the courier freight. If you need to test a longer piece, 500 mm and 1000 mm sample lengths both work.

Grades, certificate and test data

What alumina grades do you make?: Our standard grade is C799 alumina, 99.5% Al₂O₃. We also make 95% white alumina, which we supply where a drawing names C 610. We confirm the grade and maximum temperature for each part in its quotation, and our grades are compared here.
What is the maximum temperature of your tubes and crucibles?: In air, our corundum tubes are used up to 1,750 °C hanging vertically and 1,650 °C lying horizontally, and our crucibles up to 1,650 °C. Vacuum, load, fast heating and alkali vapour bring the limit down, as the alumina maximum temperature guide explains.
Our drawing says C 610. What do you supply?: We supply 95% white alumina or our standard C799 alumina instead. Neither is mullite; the grades guide shows which suits your thermocouple and atmosphere.
Do you make zirconia or porcelain crucibles, or combustion boats?: We make alumina: crucibles, boats and lids in alumina, used up to 1,650 °C in air. We don't make zirconia or porcelain crucibles, or combustion boats and tubes for carbon-sulfur analyzers. When alumina is the right choice is in porcelain or alumina crucible and alumina or zirconia crucible.
Are you ISO 9001 certified?: Yes, for protection tubes. Our ISO 9001:2015 certificate, registration 06525Q02034R1S from CFL Certification Center, covers the manufacturing of ceramic protective tubes for thermocouples and is valid to 5 August 2028. The certificate is on our quality page.
Do you have a lab test report or certificate of analysis?: An independent lab, Chinalco Testing Technology (Zhengzhou), analyses one of our alumina tubes every year: 99.55%, 99.57% and 99.61% Al₂O₃ in 2024, 2025 and 2026. The 2026 report is on our quality page, and the earlier reports are available on request.
How do you inspect the tubes?: Outside and inside diameters are checked with 0.02 mm vernier calipers. Put the tolerances that matter on your drawing and we confirm them in the quotation.

Packing and shipping

How are parts packed for export?: Tubes are bubble-wrapped or bundled in stretch film, with foam end-blocks and foam sheets between layers, in foam-lined plywood crates that are strapped and stacked on pallets. Small insulators go in 1 kg bags inside foam-lined wooden boxes, and crucibles sit one per cell in a foam grid. We confirm packing and marking for each order.
Where do the parts ship from?: They're made and packed at our factory in Tangshan, Hebei, China. Put your destination country and the Incoterm you want on the request.

The factory and how to ask for a quote

Are you a factory or a trading company?: A factory. GY Alumina is the export brand of Tangshan High Aluminum Corundum Industrial Ceramics Factory (唐山市高铝刚玉工业陶瓷厂) in Hebei, and the parts on this site are made there. See the factory.
How do I request a quote?: Use the quote form or email sales@gyalumina.com with the size, grade, length and quantity, plus a drawing if you have one. We reply within one working day.

Sources

CFL Certification Center certificate register: our ISO 9001:2015 certificate 06525Q02034R1S (shown valid when checked on 6 October 2026)
Our own figures: the factory’s standard-size list, 2026 orders and test report, as recorded in our product catalog.

Buyer FAQ: minimum order, lead time, stock, samples, ISO 9001 and test reports