Our counterweights are precision machined from 303 stainless steel. The weights slip easily onto the counterweight shaft and are secured in position with a large hand knob/brass pin assembly. The brass pin will not mar your shaft. Please note that that they no longer have a brass bushing. 

Keep in mind that you can adjust the position of the weights to counterbalance varying loads. However, the addition of a guidescope, camera and other heavy accessories may necessitate an additional counterweight. If you plan to mount your Catadioptric, Newtonian or any other scope, figure that you will need a counterweight total equal to approximately 90-125% of the weight of your tube assembly and accessories (large diameter scopes require a higher percentage). The  and  mounts require slightly more weight than the older 900GTO and 1200GTO mounts.

Important Mount Balancing Note: Please read this document to understand the proper way to position counterweights when balancing your mount: 

Below are the nominal weights and dimensions of our counterweight line.

Counterweights for 1.875" Diameter Shaft - , 900, , 1200,  mounts (and  using optional shaft):
Use these dimensions to determine how many counterweights will fit on each shaft. Note that the diameter of the 24 lb. counterweight is larger than the others:
5 lb. (2.2 kg) Counterweight () - diameter: 6", thickness: 0.75"
10 lb. (4.5 kg) Counterweight () - diameter: 6", thickness: 1.4"
18 lb. (8.2 kg) Counterweight () - diameter: 6", thickness: 2.5"
30 lb. (13.6 kg) Counterweight (30SCWT188) - diameter: 7.5", thickness 2.5"

900/1100 Counterweight Shaft (M9404-B) - usable length 16.675"
1200/1600 Counterweight Shaft (M12601-E) - usable length 22.0"
9.25" x 1.875" Counterweight Shaft Extension (M12675) - usable length 8.675"