Mag Spring Storage Clip

thingiverse

It's a clip designed to store your magazine for safe and fun handling. Compresses a standard-capacity (30/20) magazine to fit snugly into tight spaces. I couldn't find an image of it, so I included a photo of high-capacity ammo instead. In all seriousness, storing a spring in its compressed state won't degrade it unless you're keeping it submerged in salt water or exposed to extreme heat.