Yes, these are functional harnesses to be used in place of a regular nylon harness. These are really fun and addicting to collect.
I am more cautious with my garments than some I have seen, for example in Petsmart I have seen some that only use an inch or two of crappy quality velcro with no allowance for adjusment or accomplishing a good grip. I use a good length of professional grade heavy duty velcro and I double reinforce D rings to the garment. Two key things to look at when you're shopping around.