Qualtech Aircraft Counterbore, Round Shank, 3/4 in Bore, 3-1/8 in Overall Length, 1/4 in Shank dia, Pilot Shank dia Compatibility: 3/16 in, HSS, Bright Qualtech DEWA/CCBR3/4 Round Shank Aircraft Counterbore, 3/4 in dia Bore, 1/4 in dia Shank, 3-1/8 in OAL, HSS, Pilot Shank dia Compatibility: 3/16 in