Seco Contractor Series Tribrach without Optical Plummet The Seco 2153-04-BLK Tribrach is a reliable, cost-effective solution for stable instrument mounting when optical or laser centering is not required. Featuring precise three-screw leveling and a standard forced-centering base, it provides dependable performance for a variety of surveying applications. Key Features • No optical plummet – ideal for external centering methods • Three-screw leveling with center line alignment • 8-minute circular vial for accurate leveling • Standard three-prong forced centering • 5/8” x 11 base thread • Durable construction for everyday field use, not suitable for Trimble S Series Total Stations