Hi,
I use Slastix tubing. They are more expensive but last WAY longer. After I had a "regular" band snap and hit a pregnant lady in the stomach (nothing serious but she also could have fallen as she was doing rows), I only use covered tubing to assure safety. For people's at home programs or corrective programs I buy boxes of flat tubing and cut the necessary length.
I still have some regular tubing that I use for outside training but only with bootcamp type clientale.
Slastix™ - Stroops.com
Salut!
Kaisa