Trimble Base Station Extension with Height Measurement Lever Simplify accurate GNSS base station antenna height measurements with this genuine Trimble base station extension . The 0.15 m (15 cm) extension raises the receiver to provide clearance for its internal UHF radio antenna, while the integrated measurement lever provides a defined point for measuring slant height from the survey control point. Key Features 0.15 m (15 cm) extension raises the GNSS receiver above the tribrach and base station mounting hardware. Integrated height measurement lever provides a defined reference point for accurate slant-height measurements. Designed for base station and static GNSS setups using an extension-leg tripod and tribrach; compatible Trimble field software can calculate antenna height using the extension-lever measurement method. Genuine Trimble base station accessory, also supplied as a component of select Trimble Base and Post-Processed (PP) kits. Compatible With Trimble R Series GNSS Receivers: R980 , R12i ,  R580 Legacy Trimble GNSS Receivers: R12, R10, R2, R9s, R8s