Thanks OldMachinist, that pretty well clears it up for me. I was wondering where my 530 fell into the mix. It is about the right size for use on my 10 acres. Seems I find new uses for it all the time. I've found it to be a lazy man's friend.If you look at this post you'll get some idea of what the numbers mean. http://www.skidsteerforum.com/DesktopDefault.aspx?tabid=54&frmView=ShowPost&PostID=24636