TL;DR Version - DO NOT BUY THESE FOR A D-BOYS RK-10!!! Save your money and buy high caps.
Alrighty then, let's get started. I bought this for my D-Boys RK-10. When the box arrived from the UPS guy, I noticed that there were embedded BBs in and outside of the box. Since I like AirsoftGI, I will give them the benefit of the doubt. So I open the the box of magazines and and try to load the first one with BBs... none would go in. So I take the second mag out, load with BBs and attempt to insert the mag. It took a couple of tries, but I got it in. Every other round was a mis-feed. When I took the mag out, I noticed the hole in my gun where the BBs fed into looked scratched and warped. After giving up on these mags I tried to load the metal magazine that my gun originally came with; it didn't fit anymore. After 1.5 hours of panic and tinkering, I got them to fit again. Don't buy these for an RK-10. I can't take them back because I took apart the broken one. Don't make the same mistake I did.
Hard plastic, made me sweat trying to take the broken mag apart to figure out what was wrong with it.
One magazine was already broken.
NOT for D-boys RK-10.
Rating: [2 of 5 Stars!]