Explore Scientific 3x Focal Extender1.25in Barrel. 25in Barrel 3x Focal Extender. The Explore Scientific 1.25in O.D. Barrel 3x Focal Extender provides generous eye relief and is especially great for eyeglass wearers. Add versatility to your telescope with the Explore Scientific 1.25" Barrel 3x Focal Extender and get high magnification. Specifications for Explore Scientific 1.25in O.D. Barrel 3x Focal Extender: Barrel Size: 1.25" Length: 93mm Width: 45mm Weight: 249 grams; 8.7 oz Package Contents: Explore Scientific 1.25in Barrel 3x Focal Extender 3x Focal Extender; 1.25-inch O.D. Fully EMD-Coated on all air-to-air lens surfaces with all lens elements edge-blackened