Keep track of your tiny, essential, $10 MagSafe 2-to-MagSafe adapter with this handy sleeve. Includes a hole for threading a ribbon/string/wire through (ie, to attach to your keychain).
Thought up by blprnt, designed by AKA
Even with 70% infill, this takes 5 minutes to print out on a Replicator. I recommend between 50 to 70% infill (the more infill, the harder it is initially to squeeze the piece around the adapter, but the more sturdy overall).
I printed with 2 shells, since the narrow clearance between inner and outer walls made me nervous about durability.