Barbed inline straight and reducing hose connectors, straight and reducing joiners, 45, 90 and 180 degree elbows, 90 and 45 degree reducing joiners, a corrugated pond hose joiner, a washing machine and dishwasher drain waste hose joiner, PU ducting male and reducing connectors, and round and square plastic ducting vents.

For low-pressure water, ducting, pond and general-purpose work where there is no significant heat and cost matters. Plastic will not corrode, which is an advantage in wet and outdoor use. For anything pressurised, hot, or carrying fuel or oil, use aluminium, stainless or silicone instead - plastic has neither the temperature range nor the strength.

Match the barb outside diameter to the internal diameter of your hose. The hose should need a firm push to go on - warming the end in hot water makes a tight fit far easier. If it slides on loosely, it is too small and will leak or blow off no matter how hard you tighten the clip.

Yes, on anything that sees pressure or that matters if it comes off. The barb resists pull-off but does not seal on its own once the hose relaxes with age and temperature. A stainless worm drive or mini clip over the barb is cheap insurance - particularly on a pond or washing machine connection where a failure floods something.

Joining corrugated pond hose, which a standard smooth barb does not grip well because of the corrugations. It is shaped to engage the corrugated profile properly. Use it with a stainless clip at each side - a pond hose that works loose can empty a pond, which is a considerably worse outcome than the cost of the fitting.

For low-pressure air, in the smaller sizes, with proper clips - but be cautious. Compressed air stores far more energy than water and a plastic fitting failing under pressure fails abruptly. For workshop air lines and tool feeds, use proper air fittings and rated hose. Plastic barbed joiners are best kept to water and ducting.