I bought this product after I bought a cheaper versions of resistant bands from a well know on-line store to use with P90X. The cheaper bands did not last one session - and the heaviest weighted one split. I read up on why this might have happened and came across Elastitone bands, which were produced in a different way to produce a much higher quality band. I've now been using the bands for 3 weeks and they are infinitely better than the ones I'd bought before. The positives are (1) they have a protective covering - presumably if they do split they're less likely to ping into your eye, (2) the door jam is far superior to the other brands, it doesn't damage the paintwork (3) the hand grips are far more comfortable (4) the weights that they purport to be, seem to be more realistic that the other bands (which were grossly over-exaggerated on the website). The downside is that they are heavier and bulkier. I intend to take the bands with me when I work away, so this makes transporting them a little more difficult. However, I would rather have heavier bulkier bands and a proper workout, than cart around a completely useless cheaper variety. The other downside is that the starter kit comes with just one set of handles for 5 bands. Beware if you are using P90X you don't always have enough time to swap between bands between exercises, so be ready to press pause, or buy another set. I'm female, so as recommended I bought the starter kit that only goes up to a heavy band. I'm already considering getting the extra-heavy band as I think I may need it shortly - I've had no use of the extra light band so far.