A short straight length of reinforced silicone hose used to join two pipe stubs of the same diameter - metal pipework, an air filter to an intake, or a hard pipe to a component. Being flexible, it also absorbs a little vibration and takes up minor misalignment that a rigid joint cannot.

Coupling hose from 13mm to 152mm internal diameter across 29 sizes, in 20 lengths from 50mm to 950mm, in blue, red and black. There is also an off-cut mixed box of assorted short sections in mixed diameters, which is a cheap way to keep spares on the shelf.

Long enough that at least 25mm of pipe is engaged at each end on smaller bores, and more on larger ones, with the clip sitting over the supported section. That makes 50mm the practical minimum. A 75mm or 100mm gives a more secure joint if you have the room.

No - stretching a connector over an oversized stub gives an uneven seal and a joint that creeps loose. Use a reducer, which is moulded with a proper tapered transition. We stock straight reducers in 61 size pairings from 12mm to 8mm up to 127mm to 102mm.

Built to SAE J20 R3 with a smooth extruded silicone inner layer, polyester braid reinforcement and a silicone outer, 3 or 4 ply depending on bore. Rated -50C to +250C. Like all standard silicone it is not suitable for fuel or oil - use the fluorolined range for those.

A small amount, which is one reason to use silicone rather than a rigid joint. But do not rely on a plain connector to bridge a significant offset - it puts the joint under permanent stress and it will eventually leak. Where two pipes genuinely do not line up, use a hump connector.