Visit Tractor Mike website: http://asktractormike.com/ Subscribe to YouTube Channel: http://www.youtube.com/user/thebigrockranch?sub_confirmation=1 Visit Facebook Page: https://www.facebook.com/Ask-Tractor-Mike-312112962245304/ If you've never been around tractors you may not know that there are different sizes or "categories" of three point hitch pins that implements have. In other words, the pins that go in the top and lower link arms of the tractor may be different sizes, and there's overlap where the tractor or implement could be either one of two different sizes. This will be a little clearer after watching the video. Basically, most of the tractors and implements that you'll likely be dealing with will either be Category I, which has top link pins that are 3/4" diameter and lower link pins that are 7/8" diameter, or Category II, which has 1" top link pins and 1 1/8" lower link pins. Between 40 and 45 hp, the manufacturer can make the tractor either size and be within American Society of Agricultural and Biological Engineering (the group that set the rules) standards. The problem arises if you're trying to put a Category II implement on a Category I tractor. If you're there you'll have to change pins in the implement. Putting a Category I implement on a Category II tractor is real easy. You'll just have to get some sleeves from your local dealer to go over the Cat I pins and they'll be Cat II. You don't see Category III implements generally until you get up over 100 hp, but they'd be acceptable on an 80 hp tractor. There's a Category IV on giant farm tractors that you'll never see unless you're in a heavy row crop application. There's also a Category 0 on the smallest of lawn & garden type tractors that's pretty rare. I feel like I ought to be giving a test now. Class dismissed!