The leg curl machine at my college gym has the stack and normally do about 150-180 or so, but the lying leg curl set up at my local gym is much different as it doubles as a leg extension one as well (you can switch the attachment), so you have to manually add plates to it and I work up to 100 lbs on that for my working sets. The 100 lbs. on the local gym one feels a lot heavier than the 170 or so at the college one. Could just be the designs of machine, but still that's a pretty big difference. Same thing with the leg extension at another college I went to I could max it out and do sets with the "320" on it, while at my local gym, the leg extension I do my sets at is around 150-180 or so.