Mondego FB 4

The Deuter Mondego FB 4 is a slim frame bag that sits under the top tube and turns the empty space in your frame into 4 litres of storage. It weighs 160 g, mounts without tools and keeps tools, food and a phone in reach without a backpack.

Who it's for

Riders starting out in bikepacking, touring cyclists and gravel riders who want their kit on the bike. Deuter rate it five out of five for road, gravel and touring and four for bikepacking. Pair it with a saddle pack for an overnighter, or run it alone on a long gravel day in the Scenic Rim.

Fitting it to your bike

Four double hook-and-loop straps wrap the top tube and the down or seat tube, and adjust to a wide range of frame sizes and tube diameters. The bag is 40 cm long and 13 cm tall, so check your main triangle has that much room under the top tube, and whether it clears your bottle cages. Pack it so the load sits evenly, and add a strip of protective film or foam where the straps touch the paint to stop grit wearing it dull.

Capacity and what fits

4 litres takes a pump, tube and tyre levers, a multitool, snacks for the day and a light jacket, with the zipped side pocket for a phone, cash and keys. The recommended load is 1-3 kg; keep heavy items low in the bag. Gear loops on the outside take a light or small extras.

Weatherproofing

The main fabric is a 420D polyamide with a double PU coating rated to a 1500 mm water column, so showers and road spray stay out of the fabric. The main compartment and side pocket close with zips. For a full day in heavy rain, bag your phone and electronics inside it.

Stability when loaded

Because the straps grip both the top tube and a second tube at each end, the bag stays put rather than swinging into your knees when you stand to climb. Keep the load evenly spread along its length and snug every strap before you roll out.