Seco TLV Assembly for 1" OD Pole – 8-Min Vial The Seco 5500-064-08 TLV™ (Twist Lock with Vial) Assembly is a replacement  locking mechanism with integrated vial designed for 1" OD survey poles . It provides secure height adjustment while incorporating an 8-minute vial for improved leveling precision in the field. Key Features • TLV™ locking assembly for 1" OD poles • Integrated 8-minute vial for precise leveling • Compatible with standard 1" diameter survey poles • Includes mounting screws