Unique designed replaceable collet for 4200 Rotary Tool with EZ Change mechanism This collet cannot be used in any other Dremel rotary tools</br>Grooves designed around the outside diameter to identifies collet size (see 4200 Tool Manual for reference)</br>EZ Change collets are not compatible with the 225 flex shaft attachment and the 575 right angle attachment</br></br>Product Description</br></br>This hardened steel collet is specifically designed to work with the 4200 EZ Change mechanism and no other rotary tools.</br><br/>http://www.amazon.com/gp/product/B00SWIHD0W