... 3)Caliber:21mm 4)View field:2-0.9 degree Compact Pocket-Sized 15-55x Mini Zoomable Monocular TelescopeWanna see the ... , it will give you a wonderful world....Features:* Mini shape, compact design* Suitable for Golf, Scope, Camping, Hiking, Fishing, Birdwatching, Concerts ... aperture: 21mm * Objective caliber : 21mm * View field: 2-0.9°* Line field: 20m/1000m * Lens Material: Bk7 * Size: 106Φ33mm * Net ...