Spears and shafts have a few varying factors: tips, barbs, thickness, length, tabs/notches, holes and the rear end of the shaft.
In general most people prefer to have a 40cm overhang on their spearguns, so if you have a 90cm speargun you will be using a 130cm spear. You can also use a slightly shorter spear (30cm longer than the barrel) depending on your muzzle. Most people using roller spearguns prefer a shorter spear but generally a slightly thicker diameter.
If you start using a thicker spear be aware that you might need to redo your rubbers to take into account the weight of the thicker spear.
Stainless steel is a great material for spears in that it doesn’t rust but it’s prone to bending as it’s a soft metal. The most common shaft is a heat treated spring steel shaft. They are far stronger than stainless steel but their downfall is that they are coated and once that coating wears off they rust incredibly fast.
One of the best ways to maintain your spear is to wipe them down with a cloth and some normal cooking oil after you have washed your gear. Once your spear has been bent I’ve found it near impossible to try and straighten it, and even if you do they end up bending at the same spot again as it has been weakened there.
When going on a diving trip/holiday I’d recommend taking along a few spare spears in case you bend or lose one.
