What a great answer to an age-old problem! Excellent choice supplying several in a bag.
At first glance, they seem a little thin and "cheap", but they do work surprisingly well... (I'm hoping to get the "D &E" stands next.)
I see maybe one "issue"; Most of my rockets are old, and have a metal clip to mount the engines. When placed on the stand, it would be nice to have a small cutout to fit the clip in... I mean, I'll just grab my Dremel and make one, it would just be nice not to have to!
Also, a little worried about mphabib's review. I plan to use the plastic retainers for every build from now on... That would be a bummer if it doesn't work!
(I would imagine when developing these items, you would do a focus group with some master modelers! just sayin'.)