Features:Good quality aluminum alloy housing is durable for years of use. Premium optical lens helps transmit more light for clearer view.It can shorten the focal length by 0.5X and increase the field of view, usually used for a longer focal length telescope.The reducer has standard 1.25 inch interface with M28.5x0.6 thread, it fits onto the nose of any 1.25 inch eyepiece.Can both have a filter attached and be threaded onto an eyepiece or camera for more uses.It is not recommended for very fast scopes or very wide angle eyepieces.Specification:Brand: DatysonColor: BlackMaterial: Aluminium AlloyFocal Reducer: 0.5XInterface: 1.25 inch / 31.7mmThread: M28*0.6mm Size: Approx. 30 x 13mm / 1.18 x 0.51inchWeight: Approx. 0.42oz / 12gPackage List:1 x Focal Reducer