Bike Seat Stem Hidden Storage Plug – M5 Bolt & Nut Design

First, forgive the photos—they show my well-used, slightly ratty plug. That’s because it’s the exact one I use on my own bike, and it’s been through plenty of rides.

This model is designed to turn your bike’s seat stem into a hidden storage compartment. It’s perfect for tucking away small tools, emergency cash, or anything else you want to keep discreetly on hand.

The plug is sized to fit a common seat tube diameter and uses a 35 mm long M5 bolt with an M5 nut for securing. Wrapping an elastic around the outside helps keep it snug and prevents movement.

While inspired by another Thingiverse model, this version was modelled to fit my bike’s stem exactly, making it both practical and low-profile.