Just to add a bit to the Echo 1 mags - I've dropped them, stepped on them, etc and they've never broken. I suspect any fitment issues to be more due to the CA P90 than the mags. I used my mags with my E1 and a TM, and they fit just as easily and smoothly in each.
Considering the price of the E1 mags is considerably lower than TM mags, look great (although TM look better), and perform just as well, they're a winner in my book. I'll never waste my cash on TM P90 mags as long as these are available.