GMP104 Extended L‑Bar Prism – 9‑inch Coated Optical Survey Prism for Accurate Subway Tunnel Measurements

The GMP104 Extended L‑Bar Prism is a compact surveying prism designed for precision monitoring, inspection, and deformation measurement in demanding environments. Its 25.4 mm (1-inch) copper-coated prism provides a strong and reliable signal return for compatible surveying instruments.

The durable die-cast aluminum construction helps maintain stability during long-term use. The extended L-bar design provides flexible positioning, making the GMP104 Extended L‑Bar Prism suitable for locations where a conventional prism may be difficult to install.

With an approximate -25 mm prism constant, this L-bar mini prism is a practical solution for subway tunnel measurements, structural monitoring, construction surveying, and other precision inspection work.

Package Includes

• 1 × L-Bar Mini Prism
• 1 × Soft Carrying Bag

Specifications

Why Choose GMP104 Extended L‑Bar Prism?

The GMP104 combines a durable metal structure, compact optical prism, and flexible extended L-bar design in one practical surveying accessory. It is designed for professionals who need a stable measurement target in challenging locations.

Its copper-coated prism supports reliable signal return, while the die-cast aluminum body provides the strength needed for outdoor and long-term monitoring. The extended design also makes installation more flexible in tunnels, subway structures, slopes, and other restricted areas.

For surveyors, engineers, and construction teams looking for a reliable L-bar prism for tunnel monitoring, subway surveying, and infrastructure deformation measurement, the GMP104 offers a simple and practical solution.