Aqualoy immersion heaters have incoloy heating elements which have a greater resistance to scale build up than standard copper immersion heaters, offering longer life in harder water areas. They have a standard domestic water heating cylinder fit 2 1/4" BSP boss and feature dual safety protection with both a rod thermostat and a separate secondary manual reset safety cut-out. Aqualoy domestic immersion heaters are available in 11" and 27" lengths and come with a 2 year UK guarantee.