M54 Male to M48 Female Extension - 21mm

This ZWO extension adapter bridges M54 male threads to M48 female threads with 21mm of optical extension, designed specifically for large-frame astronomy cameras and astrophotography imaging trains. Constructed from black anodized aluminum, it functions as both a 2-inch nosepiece and extension spacer, allowing users to attach 2-inch astronomy filters while achieving critical back focus distances. The 21mm extension is particularly useful for full-frame ZWO cameras paired with off-axis guiders, enabling the standard 55mm back focus requirement for optimal optical performance.