This is a 5/16ths Inch Collet for Bosch Routers.  Our collets are 100% compatible with Bosch Collets used in the following models: 1604A (Only type A model), 1606A, 1613, 1613EVS, B1350, B1450, 1617, 1617EVS,1618, 1618EVS, 1613AEVS, and 1619EVS.
When you use a 1/4″ shank with a 5/16″ end mill, the shank deflects more, meaning your cut will be both less precise and less accurate.  Using a reduced shank also creates a weak point (stress concentration).
Our collet allows you to use a standard 5/16″ end mill, available for ten dollars, rather than their expensive, custom-machined 5/16″ end mill with a 1/4″ shank.
DISCLAIMER (We guarantee it fits if you have one of the routers above.  Other than that, it’s all on you): There is no suitability to any given use for this part, neither expressed nor implied.  No warranty is given of any type of use.  It will fit your router if it is listed above.  Other than that, by purchasing this collet, the buyer agrees that the total liability of the seller will not exceed the purchase price, and that buyer agrees to accept all liability for any and all uses after purchase.