Primo solid sprocket the primo solid sprocket is cnc machined from 5mm thick aluminum with no extra cutouts or unnecessary machining to help keep cost down while keeping strength up large laser etched primo logo provides a clean look and the 1516 bore includes both a 19 and 22mm adapter to fit most spindles 18 teeth features teeth 18 bore 1516 thickness 5mm adapter 19mm 22mm included weight 3oz 25t buy primo components from chain reaction cycles the worlds largest online bike