Leupold FX-I Rimfire 4x28mm Fine Duplex Leopold's classic/standard fast focus eyepiece with a low profile lock ring makes reticle focus easy to achieve and maintain Micro-friction dials are marked in 1/4-MOA increments for easy wind age and elevation adjustments Durable and compact, the one-inch main tube is lightweight and fits more legacy rings Made with Leopold's Proprietary nitrogen sealing process, which has become the industry standard Complete waterproof and fog proof integrity  each is ready for a lifetime in the field, in all conditions