The are the "generic" brand if you would of the same masks, fins, snorkels and gear that other companies sell albeit with a different logo and some minor variations. In some cases these variations are more significant and add safety or functionality (eg. the named brand company does more testing and inspection, rejecting more units perhaps than IST).
That said one of the other frustrating things about IST is how quickly their catalog or inventory changes... don't expect the same mask, fin, snorkel, etc. to be around a year from now for parts or to get a 2nd one of the same model. They turn over inventory and models really quickly. Sometimes it's 6 mos.
For the prices though they are hard to beat. I figured even if the IST wetsuit, fins, masks, etc. last only 1/2 as long I will get my monies worth. So far my 5mm wetsuit is holding up pretty darn good -- has about 100 dives in 3 years and while there's some minor wear and some places have come unglued, it's mainly cosmetic or easily fixed with some aquaseal.
That said do I buy all IST stuff... nope, don't like their lights and accessories that much -- I really think they are cheap and plastic-y. Had one of their early BC which I loved for it's simplicity and low cost. They have newer and fancier ones now with weight integration, quackers, etc. -- too much fluff and not great fit / finish. So no more IST BCs for me.
Masks, fins, snorkels, bags... yep you betcha.
