hese are the later A+ type spec which rover superseded to when upgrading the idler gear material on injection cars. See workshop manual for shimming details.The idler gear in all Mini power units must be set with great care. The thrust washer comes in various thickness to allow for accurate setup. this one is .136 137"Quantity required is 2 per gearbox but the idler gear requires shimming for correct clearance 3-6 thou as per workshop manuals but 3 thou for road and 4 thou for race is found to be reliable.