The idea of this minimalist wallet originated from the wallets with elastic bands. However, elastic bands are in some way problematic. They loose their elastic properties in short term which make the wallet non-secure.

Prior to using this "Seatbelt Webbing Minimalist Wallet", I was solely using 2 cm long inner bike tube as a band to hold my cards and money. Although it was very secure, it was nearly impossible to take the upmost and the bottommost cards because of the ultra-grippy nature of the inner tube. After a while, once I was using a seatbelt webbing for another project, the idea to use the seatbelt webbing as the main compartment popped into my mind. The slick surface of the webbing could ease the sliding of the cards in and out. Grippy nature of the inner tube would still securely hold the cards from their edges, since they were not covered by the webbing.

This wallet is very easy to make, and comes without any cost.

Step 1: Tools & Supplies

You'll need the following:

Bicycle inner tube (of a 2.2" MTB tire)
Seatbelt webbing
Scissors
Lighter

Step 2: Cut the Seatbelt Webbing

Cut approximately 20 cm of the webbing using the scissors.

Step 3: Seal the End of the Webbing

Use the lighter to seal the edges of the webbing to prevent fraying

Step 4: Cut the Inner Tube

Cut approximately 5 cm of the Inner Tube using the scissors. When cutting, try to cut with a single scissoring motion to obtain flat ends.

Step 5: Turn the Inner Tube Inside Out.

Turn the inner tube inside out, as inner surface of the tube is more esthetically pleasing than that of the outer. Slightly grainy surface of the inner part would give a better appearance.

Step 6: Wrap the Inner Tube and the Seatbelt Webbing

Wrap the webbing lengthwise around the cards. Leave the approximately 1/4 of the cards uncovered.
Wrap the inner tube to secure the webbing and the cards.
On the top, align the inner tube so that approximately 1 cm of the webbing is uncovered. This uncovered portion will serve as a flap holder.
Use the extended portion of the webbing under the cards as a flap to cover the cards completely.

Notes

The length of the inner tube will have a significant impact on the tightness of the cards. If it is too long, it will be very hard to slide the cards in and out. You can use a short (2 cm) tube and it will still securely hold the cards. However I opted to use longer (5 cm) tube to achieve a better looking and more protective wallet. Try and find your length.
I used inner tube of 2.2" MTB tire and it is already tight round the cards. I'm not sure if it will work with RoadBike tires, since they are narrower.
Bicycle inner tubes are very durable and has long lasting elastic properties so this wallet is nearly indestructible and will last long.
You can also put your keys and some coins inside.