Falcon the Manufacturer BT40 Tool Holder. Our Collet was made from Alloy spring steel and fully hardened these ER collets. We designed a product for good holding, which gives a great for work holding in small lathes. The product comes in different sizes like in ER-16, 2 to 10 mm in steps of 1mm, 17, 27.5, ER16 8mm. ER-20 comes with 2 to 13 mm steps of 1mm.