Six slotted set screw fixing to standard 1/4" solid shaft pots. Knob has a sturdy brass insert inside threaded for the tiny brass set screw. Very dark brown phenolic plastic knob features a gold aluminum top cap with black indicator line. I measured .770" diameter at the bottom, .616" overall height, .625" diameter on the rim of the gold cap. The knobs on my '65 JTM 45 measure .542" diameter on the rim of the gold cap. Bonus! Some of you have told us that you prefer a hex head fixing screw and wrench so we include this also. Set of six knobs.