Features: *Easy and uncomplicated replacement suitable for all conventional radiators with 1/2 inch thread. *Works with swelling discs - when in contact with water, the discs swell up to prevent leakage. *Saves heating energy through continuous and automatic bleeding of radiators. *It has a shut off cap that can be used to stop auto venting if so required. *Product has got 3 operating modes:1. Middle knob fully screwed in - automatic venting (it will shut off automaticaly when there is no more air in the radiator).2. Middle knob partially screwed in - vent open. *Middle knob unscrewed - vent closed. Specifications: *Size: 1/2" BSP. *quantity:1/2/3/4/5pcs *Item dimensions:L x W x H 27 x 26 x 26 millimeters *Style:vent valve *Controller type:ring Package Contents: 1/2/3/5pcs vent valvefor you choose Note: 1. The real color of the item may be slightly different from the pictures shown on website caused by many factors such as brightness of your monitor and light brightness. 2. Please allow slight manual measurement deviation for the data. _x000D_