The left hand lifter size 42mm is needed for 2-valve engines equipped with a high-lift racing camshaft. This is a hydraulic lifter that can be modified to a lower weight mechanical lifter. The picture lacks a 40mm hydraulic lifter for Mercedes that can be used for 2-valve engines, replacing the original 38mm lifter which is extremely expensive. For the 40mm lifter, the bores in the cam housings have to be altered. The same goes for the 37mm and 38mm mechanical race lifters for the 4-valve engine