Restube trigger protector
The Restube Trigger Protector is to protect the trigger mechanism while you distance swim with the RESTUBE self inflated by blowing it up. Simply remove the cartridge and screw it in.
Some swim races are mandating the use of inflated buoys, also called 'drag buoys'. The RESTUBE can be just that, self inflated by blowing it up in about 5 breaths. Many swimmers also use the inflated buoy during training, as this will provide better visibility for other people on the water like paddlers, boats and lifeguards and will save you the weight of the CO2cartridge.
This is not mandatory but recommended if this is a normal part of your training.