Got one of these myself last summer. Needed a chest protector to wear while I was riding off-road trails. I'm not very easy to fit, cause I'm short and wide, and went with a XXl size. The fit is good, the Lycra allows the pads to stay in place. There are straps that help to snug up the upper and lower arms. The belly band, well, er, is stretchy. Everything stays in place once donned and snugged down. I wear the body armor with a riding jersy on top to keep it from snagging on branches and stuff. Sometimes wear a Camelbak MULE on top of the jersy/armor setup and it fits without having to extended any straps. Also, I tried it out on a few summer road rides when it was too hot for a jacket. I felt comfortable cruising the back roads at 55-60 mph with it on. Any faster or busier roads, I'll wear a proper jacket.
I haven't crash tested it yet, but think it is okay for a few low speed get offs, but anything major will be a "one time" event for the armor. But isn't that its purpose anyway?