Tubular tyres have the inner tube permanently stitched inside the casing. They are held in place using glue or glue-tape, and are affixed to rims which lack the sidewalls characteristic of a hook-bead rim. Tubulars take very high pressure which reduces their rolling resistance, and can result in wheelsets that are lower in overall weight than comparable clincher wheels. They can also be ridden at lower pressures than clinchers without the risk of pinch flats, because of the shape of the rim. This makes them well-suited to cyclo-cross, especially in muddy conditions where low tire pressures are used. Also called sew-ups, tubies, or tub.