BuildMyGravelBike checks wheel size (700c/650b), thru-axle fit, freehub vs cassette, brake caliper mount vs frame/fork (flagging a documented I.S.-to-post-mount adapter path where it applies), tapered steerer, BB shell/spindle, tire clearance and drivetrain system/speed/actuation as you pick parts. A green dot means no conflict among the dimensions we check. Some makers publish no spec data, so it's not a guarantee of perfect fit.