The 3M is rated 3-6 but will throw 8 in a pinch.
The 5M is rated 6 to more than you'd ever want to throw
I have both the 3M and the Harrington 542. The 3M is actually stiffer, and a few ounces lighter. If you really want to throw heavy weight, the Harrington to check into is the 552---order a back brace while you're at it
