Notes on sizing - The aperture size is the inner diameter of the cap and corresponds to the outer diameter of your telescope tube. Measure your telescope outer diameter before purchasing. Caliber - Different inner diameters meet your various needs: 25.5 mm, 28 mm, 30 mm, 34 mm, 35 mm, 36 mm, 37 mm, 38 mm, 39 mm, 40 mm, 41 mm, 42 mm, 43 mm, 44 mm, 45 mm, 46 mm, 47 mm, 48 mm, 49 mm, 50 mm, 51 mm, 53 mm, 57 mm, 58 mm, 59 mm, 60 mm, 61 mm, 62 mm, 64 mm, 65 mm, 66 mm, 67 mm, 69 mm. Lens caps - Lens caps are sold in individual pieces. Material and durability - High-quality plastic material, durable and not easy to break. Why you need this - Protects telescope optics from dust, moisture, and scratches during storage, transport, and field use. - Wide range of sizes ensures a precise fit for many common telescope outer diameters. - Purchasing single caps lets you replace only the sizes you need, reducing waste and cost. Use scenarios - Field observing: cap the telescope tube when moving between locations to keep dust and debris out of the optical path. - Storage and transport: keep each cap on to protect optics inside cases or drawers. - Maintenance and cleaning: use the appropriate cap to prevent contaminants from entering during servicing.