for their machines, mine is a horse'n a half and I believe it is 5/8?? I'll go out and measure this morn if you like. And on your question about the Little Giants: I have found a big difference in the two sizes when I actually had the experience of a 50lb. once, it definately moves more steel but at a slower cycle of blows. My 25 is a super little hammer but it just won't hardly take a 3 inch bar and allow you to draw out some nice .292 or so blade stock. It just depends on what your trying to do with it. I guess the deal is, for the most part, a 50 will "make" you some stock whereas a 25 will "work" ready made stock. I'd be iterested in what others have to say here.
regards, mitch