Highly Optimized Gear' or HOG manufacture a small, low-profile finger spool. Finger spools can have a variety of uses, the two most common are D-SMB (delayed surface marker buoy) deployment and searching for a lost line, object / anchor or diver.
Finger spools are becoming a more common sight as recreational divers begin to adopt this piece of equipment. It is possibly because a spool is ideal for stashing in a pocket or clipping to a D Ring.
The HOG finger spool is manufactured from ABS plastic. The holes along the side can be used to lock a marine grade 316 stainless steel double ended bolt snap to the spool. Alternatively the diver can make a small loop, sometimes known as a 'Jasper' loop, at the end of the line. This is then threaded through one of the holes and the bolt snap attached to the loop, to stop the spool unwinding.
The 30 metre / 100 foot bright orange #24 line makes it easier for the eye to follow, when diving in low visibility conditions. The line most commonly used for finger spools is #24 braided line, some people call this 'cave line', as opposed to 'wreck line' / #26.