SVBONY SV135-This is definitely a must for beginners to start a good eyepiece collection.with this eyepiece, you can enjoy planetary astronomy .As a beginner; SV135 is good for starter astronomer! Zoom from low to high power in an instant with SV135 versatile eyepiece Zoom Eyepiece; 7mm-21mm linear continuous zoom; give you more flexibility with out changing eyepieces;Very easy to use and very smooth operation. 1.25" barrel size; Compatible with any telescope that accepts 1.25" eyepieces;1.25" aluminum barrel is threaded for filters and internally blackened to eliminate internal scattering