Aluminium beaded and unbeaded straight joiners and T-pieces from 8mm to 102mm; aluminium elbows in four angles; silicone couplers, hump connectors and T-pieces; fluorolined silicone couplers for fuel and oil; rubber coupling joiners from 5mm to 102mm in short and long lengths; plastic barbed straight, reducing and angled joiners; and PU ducting connectors.

A beaded aluminium joiner with T-bolt clamps. The bead gives the clamp a mechanical stop so the hose has to physically stretch over it to escape, rather than relying on friction alone - which is what stops a joint blowing off under pressure. Unbeaded joiners are for coolant, breathers and low-pressure air.

Metal for a rigid section that holds the bore round under pressure and looks tidy. Silicone or rubber where you want flexibility, vibration absorption and a bit of tolerance for misalignment. Plastic for low-pressure water, ducting and general use where cost matters and there is no heat. Match the material to pressure, temperature and medium.

The raised hump absorbs vibration and takes up slight misalignment between two pipe stubs without passing that movement into the rest of the pipework. Use one wherever an engine moves relative to a fixed pipe - the classic case is between a turbo and a chassis-mounted intercooler. A plain coupler in that position eventually fatigues.

Use a reducer, not a stretched coupler. We stock silicone straight reducers in 61 size pairings, silicone reducing elbows in 43, plastic reducing joiners and reducing PU ducting connectors. Stretching one hose over an oversized stub gives an uneven seal and a joint that will creep loose.

At least 25mm engaged at each end on smaller bores, proportionally more on larger ones, with the clip sitting squarely over the supported section rather than near the open end. That is why a 50mm coupler is the practical minimum for a straightforward join - a 75mm or 100mm makes a more secure joint if you have room.