I have ~500 miles on this product and no complaints. Can't even tell I'm wearing it which is a big positive.
I purchased a Large(I'm 6'-2") the shoulder straps are almost adjusted as far loose as it can. I have pretty broad shoulders and chest. Mid section strap has plenty of room for adjustment, that I'm sure I'll never need to use the full extending range of it.
If your looking for a back protector but don't want to shell out big bucks for a name brand; this is your baby. You won't be disappointed!