This Recoheat Airflow Heat Recovery System is built to fit 6" stove flues but has a wider top to retrofit to cut vitreous pipes. This allows fitting to an existing installation by simply cutting the stove pipe 75mm above the collar and replacing the section by tilting and wiggling the stove. It isn't necessary if you're retro-fitting to a stainless steel flue section as they'll fit the standard units with no problem. If in doubt, check the external flue pipe diameter with callipers - if it is more than 152mm, use one of these.
The unit is supplied with a super-silent aquarium pump with an air flow rate of 3600 litres per hour (60l/m), 1 metre of heat-resistant black silicone tube, and 3 metres of standard tubing, plus connectors.
The Recoheat is a heat pump for wood burners and solid fuel stoves. It significantly increases the heat output of your stove and how long the stove delivers heat for, and reduces your fuel consumption - all at the cost of running the 37-watt air pump - so similar to the cost of a light bulb.
Please check your flue size carefully - this is the 6" version with a wide top for fitting to a cut-pipe.