Amazon.com: 1/4 Inch Shank Router Bit Collet Extension Chuck Converter Adapter, Convert 1/2-Inch & 1/4-Inch Shank Bits with ER20 Spring Collet, ER20 M Type Collet Chuck Wrench Spanner -(Pack of 4) :
1/4'' to 1/8'' Collet Reducer | Rockler Woodworking and Hardware
Amazon.com: 1/4 Inch Shank Router Bit Collet Extension Chuck Converter Adapter, Convert 1/2-Inch & 1/4-Inch Shank Bits with ER20 Spring Collet, ER20 M Type Collet Chuck Wrench Spanner -(Pack of 4) :
1/4" to 1/8" Reducer Collet Adapter for CNC Routers - IDCWoodcraft.com