This 2x barlow lens with metal body, the lens fully multi-coated provide a sharp view; it can double the power of any 1.25” telescope eyepiece, ideal for high power observation; a brass compression ring can protect your eyepiece from marring or scratching the barrel.SVBONY SV135-This is definitely a must for beginners to start a good eyepiece collection.with this eyepiece, you can enjoy planetary astronomy without spending a lot of money.As a beginner;SV135 is great for starter astronomer! Zoom from low to high power in an instant with SV135 versatile eyepiece Zoom Eyepiece; 7mm-21mm linear continuous zoom;The field of view can be changed without changing the eyepiece;Very convenient for visual and outdoor use 1.25" barrel size; Compatible with any telescope that accepts 1.25" eyepieces.