Pains Wessex Replacement/Spare Rocket for Linethrower 250:

A self contained line-throwing appliance consisting of a weatherproof plastic casing with end cap, twist-grip trigger assembly, rocket and line. To comply with SOLAS requirements, four complete rocket and line assemblies should be carried on board. The device has a throwing range of between 230m and 250m. A solid propellant is used which guarantees a highly accurate flight path even in strong winds.

Replacement Rocket for Linethrower 250 (Tutorial):