GMC offers a selection of useful plated-steel tips for spearguns and poles. Those designated 6-7mm come with an adapter for either 6 or 7 mm shafts.
Spear Point, 3 Prong Aluminum Paralyzer
Spear Point, 3 Prong Fork, Plated 6-7mm
Spear Point, Delta Trident
Spear Point, Double Barb, Plated 6mm
Spear Point, Single Barb - Plated 6mm
Spearpoint, 4 Prong Fork, Lg, Plated 6-7mm