The Pentax SMC eyepiece is designed for use with our 65mm scopes. The eyepiece has a high-refraction, low-dispersion lanthanum glass elements to provide high-resolution images with minimal aberrations and the Pentax-original smc full-surface multi-layer lens coating to improve light transmission efficiency. Advanced computer simulation design technology was used to drastically reduce internal reflections producing brighter, clearer images. JIS Class 4 weatherproof construction make these eyepieces more durable and water resistant and has the Pentax Worry-Free Warranty.