Bought to help with a Range Rover P38 spring conversion kit. Firstly the build on these things gives confidence that they are not going to take your head off, unlike the cheaper types. Experimenting I was able to compress the spring (which is very beefy) by about 35mm without too much trouble. The issue is that this only compresses one side of the spring, curving it. I bound the compressed side wit 20 turns of paracord to maintain the compression and then compressed the other side. I could have done this with my hydraulic press but the shape of the spring holders on this thing gives one the confidence that the springs are not going to slip.