Sentry 12HE23BK: Constructed of high quality 3mm thick neoprene/nylon laminate, the Scopecoat Holographic & Electronic safeguards your optics from dust, dirt, dings, scratches and moisture. It is extremely water resistant and draws moisture and condensation away from your optic. This slim fit cover is perfect for the field. You may make it temporarily waterproof with commercial spray-on water repellent, and it is machine washable. This model is black, Size 23, which is 5.8\" long x 32mm. It is compatible with Trijicon Acog TA-01 (4x32).