Large: 5/8" length x 3/8" diameter, 1/8" hole, 1/2" 1/4-20 machine screw, slotted/Phillips. Medium: 5/8" long x 5/16" OD, 1/16" bore, 1/2" 10-24 machine screw, slotted/Phillips. Small: 25/64" long x 1/4" OD, hole 0.0689" (=1.75 mm), 3 pcs machine screw /8" 10-32, slotted. The screw hole runs the entire length of the cylinder.