The raised hump in the middle lets the coupling absorb vibration and take up slight misalignment between two pipe stubs, without transmitting that movement into the rest of the pipework. Use one wherever an engine moves relative to a fixed pipe, where two pipes do not quite line up, or where thermal expansion changes the gap. Ours are 100mm long in 25mm to 102mm bores, in blue, black and red.

Any joint that crosses between something that moves and something that does not - the classic case is the pipe between a turbo or engine-mounted component and a chassis-mounted intercooler. A plain coupler will transmit that movement and eventually fatigue a joint or crack a pipe. A hump absorbs it. On a rigid, well-aligned joint, a plain coupler is cheaper and perfectly adequate.

It creates a three-way branch in a hose run - taking a heater feed off a coolant line, adding a breather or bypass takeoff, or splitting an air feed. Ours are reinforced silicone with a 25mm spout, in main bores from 25mm to 102mm, in red, black and blue. Being silicone rather than metal, the T-piece also absorbs a little vibration.

The plain silicone cap is unreinforced, 35mm long, in 4mm to 38mm bores, and suits blanking a low or zero pressure stub. The reinforced blanking cap has polyester braid, is 60mm long, comes in 4mm to 25mm, and is rated 5 to 12 bar working pressure. If the port is pressurised, use the reinforced version - an unreinforced cap will balloon and blow off.

Two options: a standard silicone box with assorted reinforced hose sections in three colours and mixed diameters and lengths, and a fluorosilicone box with the equivalent in fuel-and-oil-rated hose. Both are 3 and 4 ply. They are aimed at workshops and builders who need short pieces at short notice, and cost far less than the equivalent lengths bought individually.

The silicone parts are built to SAE J20 R3 with polyester braid reinforcement - the same specification as our standard hose range, so temperature and pressure capability matches. The fluorosilicone off-cuts are the fuel-and-oil-rated equivalent. Standard silicone parts are not suitable for fuel or oil contact.