Yes and they are flipping awesome, I hook them round dumbells to do plyometric curls, hammer curls, and reverse curls.
Safe and easy way to improve explosive strength, a lot of power-lifters and olympic lifters train with them also for the same reason, also been using them lately for rotator cuff exercises.
Check out these guys, who also offer the more crazy hardcore resistance bands:
http://www.pullum-sports.co.uk/accessories/resistance-bands/cat_16.html Including one which offers from 80-200lbs of resistance!
Thinking about setting myself up with some to take to the park in the summer so I can train outside