The HideOut XL’s clear polycarbonate shell opens to a 2-inch by 3.5-inch cavity, IPX7-rated for a 1-meter dunk for 30 minutes, roomy enough for a key fob plus a couple of spare keys. Three neodymium magnets clamp it to bare metal — a truck frame, a porch railing — and a 3M VHB adhesive plate ships in the box for surfaces magnets won’t grip. $16.99.