Description The perfect fusion of speed and knock-down power - Rob Allen 7.0mm Double Notch Speargun Shaft. The world record winning Rob Allen 7mm Double Notch pearguns shaft, an excellent general purpose spear for all occasions. All Rob Allen shafts are made from oil-quenched carbon spring steel (1950 mpa), cut to a tri point, and zinc plated to combat corrosion. Best with single 20mm or Twin 16mm rubbers.