Rubber and shaft calculator.

Rubber diameter. 14 mm is the all-rounder for reef work and a balanced load. 16 mm is the standard for mixed and bluewater with comfortable loading. Moving to 18 mm buys you penetration on heavy fish but adds noticeable loading effort and shoulder fatigue.

Double bands. From 90 cm upwards, or for bluewater at any size, a second band transforms the shot. The rule of thumb: double up when the gun is 90 cm or longer, or when the target fish exceeds 10 kg at a regular distance past 2 m.

Band cut length. Band length × 3.2 is the stretch target. For a 75 cm gun with a typical geometry, a 53 cm band stretches to around 170 cm when loaded. Cut shorter for more power, but not below band length × 3.0 unless you are an advanced loader.

Shaft diameter. 6.5 mm pairs with single 14 mm. 7 mm is the bread-and-butter for 16 mm singles and light doubles. 7.5 mm for 16 mm doubles and most 18 mm setups. 8 mm for the heaviest bluewater rigs.

Need a hand? Message me with your gun model and I will confirm the spec before you order.