My boys recently got a tube of those M&M minis. The tubes are red plastic, and have a resealable cap that is attached to the tube body. I initially wondered if I could use them in a rocket, but then I discovered they were the perfect size to hold 2 D engines. I don't own one, but they look like they might be about perfect to hold a 24mm RMS casing. Someone that has one might want to try it out.