A double roller setup can effectively be used as "two spearguns in one". Using a quickly removable knot, a hunter can easily remove one of the bands and use the speargun as a single roller. This is helpful when encountering poor visibility, or hunting in rocks and reef. When conditions require longer range, the band can be added and the speargun used as a double roller. 
 
The double roller muzzle for spearguns is made of fiberglass-reinforced nylon. With larger wheels on the front, it allows the bands to lay and function with less interference during the shot. It features a bridge to secure elastics after firing and can accommodate up to 15mm bands. It’s suitable for tubes with diameters from 26 to 26.7mm. 
 
Bridge on top of muzzle stops wishbones and ensures and no interference with the accuracy of the shot. 
The overlapping system is made possible by two different pulley sizes: a front pulley with a diameter of 36 mm and a rear pulley of 28 mm. This system provides smoother and more efficient operation. 
The muzzle can accommodate elastics up to 15 mm wide, providing sufficient power for various shaft diameters.
It is designed to be suitable for tubes with diameters ranging from 26 to 26.7 mm, offering versatility for use with different types of spearguns.
Ceramic bearings can be added.
The front of the muzzle can accept a threaded shark spike.