This is our M30 BB for installing a Praxis M30 crank into a BB86 Road frames, a BB90 MTB frame or BB92 MTB frame. For Praxis M30 spindle based cranks only. NOT for other 30mm cranks Used only for frames that are BB86 ROAD | BB90 MTB | BB92 MTB Unique all in one design in which the bearing outer race is also the outer press fit surface Chromium steel design. Steel Bearings | 30mm Drive bearing /28mm NonDrive bearing Before installing, you must use Praxis frame Gauge to check your frame. BB86 Road/BMX = 86.5mm width X 41mm diameter BB90 MTB = 89.5mm width X 41mm diameter BB92 MTB = 92mm width X 41mm diameter