I had the two gold ones, which I believe were Gaia and Saturn. For the 300 yen i paid for each after a sale, they were worth it.
They're made of a very, very soft plastic, seeing as how they have to be to facilitate the gimmick. You buy them as a Frame, then you snip all the individual pieces apart. Then, since all the pieces have pegs and holes all over them, you can plug them back together their frame mode, which looks, unsurprisingly, like a model kit frame.
Aside from molded-in detail, a lot of which is missing due to hollow parts, the coloured details comes 100% from stickers, some of which have to go over some awkward surfaces. The biggest offender of that are the round, Planet parts in the chest of the guys. Those stickers are a bitch.
All of the joints are plastic on plastic, instead of any polycaps being involved. For a super-cheap line, they're alright. I don't have the two I had anymore, but that's mostly because I didn't find myself doing much with them, not because I thought they weren't worth it or anything.
Don't go in expecting too much and you should be fine.
