Great buy for the price!
They stretch out quite quickly, seems like after just 2-3 uses.  But, you can keep using them after they stretch, you just have to wrap it an extra time or two. I imagine they will eventually stretch until they're no longer usable, but with quantity if 300; these will last a very long time!  And, it's super convenient to have so many that I can put the bands in random places (cars, desk, purse, coat pockets,etc.) and always have one when I need/want it.
Rating: 4 stars