For sizing I got the L/XL. I measured diameter of upper arm (about 4” above elbow) & I’m about 12.5” The S/M felt a little bit restrictive in terms of elbow flexion & though I’m sure they would’ve softened/stretched I chose the L/XL because they offered more surface area coverage around the elbow & to me feel safer considering how the differing elbow strikes land with slightly different points on your elbow.
The reasons I gave 4 instead of 5 stars are that:
1) I dont like the loop as no matter which arm you put the pad on there is a slight slight chance of hooking a finger/thumb when you use small mma style gloves
2) The velcro on the strap is VERY strong & if it touches the fabric of the pad (especially anywhere at a seam) it pulls threads loose.
That said, these seem really great & safe!