The Flak Base hosts the shoulder, bicep, elbow and forearm guard protection, as well as shoulder adjustment straps. "Cheater" straps between the bicep and elbow pads allow for more exact positioning of the elbow/forearm guard protection. Thumb stirrups keep the elbow/forearm guard section from sliding up in a fall. Upper chest features a cut-in of Spandex mesh for added comfort when worn directly against the skin.
RockGardn Flak Base fitment:
The dividing line between S/M and X/L is a chest measurement of about 41". Measure your chest by using a tailor's tape (the soft kind), going under your armpits and over your pec muscles. If you don't have a tailor's tape, use a piece of string, then measure the string length with a conventional measuring tape.
If you're at the boundary between sizes, look at your basic body shape. If you have a very "V" shaped torso, go for the S/M. If you have a straight torso, and particularly if you have wide shoulders and/or big biceps, go with L/XL.
Buy RockGardn Flak Base from Chain Reaction Cycles the world's largest online bicycle store.