Depends on what you are after. For coons I use a number 1 double long spring or very well broken in #1.5 coil spring. Either one should catch a dog low on the paw with no damage. For land sets for fox or coyote, I use a 1.75 or #2 coil spring. Never caught a dog in them, but they didn't do much damage to grey foxes or coyotes. I wouldn't use a number 3 in a landset, but that's just me.