I have the compression valves on a few of my bikes. Even without extensive testing adjusting they make a positive diference. The 2 sets of Racetech units, in a 84 CR500 and a RM 370 are from brass, strong and well finished - chamfered and deburred and with alternate springs. I also have YSS set. These are made fom anodised aluminium and are thin section and look to be a bit short on mecanical strength. Service was a bit ordinairy. I was sent the wrong items but refused a return. I ended up using them on forks they were intended for and if installed according to instructions would have reduced the fork travel, hammered the valves as the spring coil bound and very likely with the damper rod mods required, pulled off on full extension.