CMT 800.616.11 Box Joint Bit with 1-7/8-Inch Diameter with  1/2-Inch Shank 3/8-Inch cutting depth, 1/21-9/16-inch thickness, 3-35/64-inch overall length 3 hi-density Carbide cutting edges for long-lasting performance Anti-kickback design to control the depth of cut and work safely For making finger joints easily. Adjust the bit height to work on different board thicknesses