Cartridge heaters are solid heating elements
that require close tolerances to last longer.
There are usually used in dies, tools, sealing blades, moulds and even ignition.
Usually they are manufactured in steel sheath from dia 6mm upto 30mm.
Other variants are possible like Angular shaped, with flange, hose protected lead wire, with thermocouple built in, etc.
Wattage density upto 25 W/cm2