Hi,
I have a lastolite Hotrod softbox and a Lencarta Profold.
The Lastolite is for speedlight and will stand up to domestic use if looked after. Definitely not industrial quality but I'm happy with it for speedlight use.
The Lencarta one is pretty good too. The carcass material is kinda thin but I guess thats the trade off for making it fold like an umbrella. I have Bowens wafer and Calumet Illuma boxes which have much thicker and better made carcasses but then again, they don't fold. Also, you can clearly see the modelling light through the material when it is on a studio light. The Lencarta website states the width as 30cm. I measured mine at 25cm wide. Having said all that I intend to buy a second one because they are reasonably priced and they do have very reasonably priced grids. I'll live with the drawbacks.
Regards...
Steve