This is  a spare filter bag for the Aquarium Power Gravel Cleaner. The main device details are as follows;

Aquarium Power Gravel Cleaner

This is a simple to use hang on aquarium gravel cleaner, incorporating a powerful water pump and an efficient filter bag made of micro-porous material to trap even the smallest of particles.

The cleaner is powered by a powerful mains-powered pump for the most efficient aspiration. The Power Gravel Cleaner makes gravel cleaning simple, without the risk of spills or leaks. All electrical parts are insulated and completely submersible, and can be cleaned under running water.

It is provided with a filter cartdridge consisting of a series of inclined planes to which dirt clings. This system allows the user to easily eliminate dirt by just removing and cleaning the foam cartridge. The cartridge is washable and re-usable.

The Power Gravel Cleaner is suitable for all kinds of aquarium, where it is possible to hang it on the wall of the tank. It can also be used on aquariums where the rim of the tank is thicker than the bracket, by partially fitting the bracket ; but the unit must be secure prior to use.

By using this method of re-circulating the aquarium water, the aquarist is able to clean the gravel thoroughly without having to change or remove large amounts of water.

Replacement filter bags also available.  

Dimensions:

Motorised Filter Unit:  Length : 150mm  Height : 150mm
Depth (front to back from rim of tank) : 75mm

Motor: 220-240V : 6w : 400 lph

Gravel Cleaner Tube : Diameter : 45mm    Length : 350mm  Hose Length : 800mm