If your 900 is frequently used as a portable mount, you may wish to consider upgrading to this counterweight shaft adapter. The stainless steel insert will reduce the likelihood that you will damage the threads by cross-threading when you attach your stainless steel counterweight shaft.
Mounts that can be upgraded: All 900 mounts including early models, except mounts with 4K or 10K Step Mounted Shaft Encoders (used with JMI Digital Setting Circles).
Installation Instructions: Simply remove the original counterweight shaft adapter and install the new one. Note that both components were designed with a through hole into which you can insert an object, like an Allen wrench, to either loosen or tighten the adapter.