This Cordura bag designed to fit one tire, a CO2 cartridge or a inflator such as the fast air. The Arundel Tubi has 28 cubic inches of internal volume. The dimensions are 7"x4"x1". The weight is 82g. There are two small side pockets for loose tools and petty cash. A single strap in the middle of the bag goes around the seat rails and then the bag. There's a genuine leather tab on the back so the seatpost won't wear through the bag. It is available with a couple of color options on the side piping.
Expensive tubulars usually fit better than cheaper ones as the casing is thinner and more flexible, so they fold smaller. Start by removing the excess air from the tire.
TUBI seat bags available in black, with colored piping, either: black, grey, red, yellow, blue, pink or white piping