Inner tube 16x2.125 (57-305) 0x90° valve

Size

16x2.125 inner tube, ETRTO 57-305: 57 mm wide, 305 mm rim diameter. This size fits electric unicycles, balance bikes and children's bikes.

Beware of the two meanings of 16 inch

The 16 inch designation covers two rim diameters: 305 mm and 349 mm. The 305 mm is used on electric unicycles, balance bikes and BMX; the 349 mm on folding bikes such as Brompton. The two are not interchangeable.

That is what the ETRTO code is for: 57-305 removes the ambiguity that "16 inch" leaves open.

0x90° valve

The valve is straight on its first segment and angled at 90 degrees on the second. This angle gives access to the valve from the side of the rim, where a straight valve would be hidden.

The angle is dictated by the rim and mudguard geometry. Check the one on the original tube before ordering: this is the leading cause of error on this product family.

Fitting

Sold individually. Inflate the tube slightly before inserting it into the tyre to avoid folds, and make sure it is not pinched between the bead and the rim before bringing it up to pressure.