Air-cooled torches are simpler and need no cooler, but their duty cycle at high amperage is limited and the handle gets hot. Water-cooled torches run cooler and hold higher amperage continuously, which is why production TIG work uses them. A water-cooled torch without coolant flow will overheat within seconds.
Torch series numbers (9, 17, 18, 20, 26) describe the head size and amperage class — 9 series for low amperage and fine work, 17 and 26 for general work at increasing amperage, 18 and 20 for water-cooled. Consumables are series-specific, so the torch series determines which collets, cups and gas lenses fit.
Flex-head and rigid-head versions differ in how the torch body articulates. Flex heads let the angle be adjusted to reach awkward joints; rigid heads are more durable and hold their angle. Cable and hose assemblies are sold separately or as complete torch packages.
