The Manfrotto MVMXPRO500US XPRO Aluminum Video Monopod is wonderful, but its tilt-lock was not strong enough when I overloaded it with a DJI Ronin-S gimbal flying a Sony a7R III mirrorless camera.

This block is designed to be inserted into the monopod head, under the bridge, preventing the head from tilting.

Designed to fill a gap that's 2-3/8" (60.325mm) tall, 1-3/8" (34.925mm) wide, with a slot in the bottom for the bump where the monopod head joins the leg.