Flexible, lightweight, soft rubber with ergonomic angled eyecups provides comfortable cushioning and reliable eye protection. Compatibility: Fits most optical devices with eyepiece diameters from 36 mm to 43.5 mm. Glasses friendly: Stretches over glasses to deliver comfortable cushioning and a secure fit. Improved alignment: Aids quick eye positioning for proper eye relief and accurate alignment with the optical center. Key benefits and features Comfortable protection: soft rubber material cushions the eye area during extended viewing. Flexible fit: diversified, ergonomic angled eyecups adapt to different eye shapes and viewing angles. Broad compatibility: accommodates eyepieces from 36 mm to 43.5 mm across most optical devices. Glasses compatibility: stretches easily over eyewear without affecting comfort or calibration. Quick positioning: supports fast and consistent eye placement for accurate viewing and eye relief. Use scenarios Birdwatching or wildlife observation: wear with prescription glasses for longsession comfort while maintaining proper eye relief and alignment. Astronomy and stargazing: compatible with telescopes and spotting scopes in outdoor conditions, helping you secure a quick, correct eye position. Field photography and outdoor voting observations: use with binoculars or monoculars while wearing gloves; easy to slip on over eyepieces and provide cushioning during extended use.