Drop in replacement for all Rob Allen Vecta 2 speargun trigger cassettes, this loading butt disperses the pressure of loading and reduces the chance of the speargun slipping off your chest while loading. No modifications needed, simply push out the retaining pins and remove the original cassette/trigger from handle. This cassette with loading butt comes with a trigger mechanism included, so there's no need to switch the old trigger mechanism from the old cassette to the new.