I won't lie, I've only pumped 10 pounds before. that Β£20 are in a league of their own. Got through some metamorphic gneiss quickly and didn't feel anything in my broken wrist (high vibrations are killer the next day) which is the only reason I bought this. They don't lie, this pen is made of fairy dust, now it's a powerful fairy, but a fairy nonetheless. If you rock this all day or have a bad wrist, this is the rocking sled without a doubt. Even after smashing the rocks, I just couldn't stop rocking. Having the power of Thor in my hands is addicting and leaves a trail of broken stones in my wake. You just get lost in the swing, Carnage Some rocks don't join your resistance cult at first. The first hits land like a stone that throws your head back (forged steel 46 HRC), but which quickly shatters. A few more strokes and all that's left is crushed powder. Yes I would buy it again but with this sucker build I never have to.