Orion 9863 11 Pound Counterweight for Atlas and Sirius Mounts Extra 11-pound counterweight designed for the Orion Atlas EQ-G and Sirius EQ-G GoTo equatorial mounts Helps balance especially heavy telescopes and instruments on the Atlas EQ-G or Sirius EQ-G equatorial mounts Ideal for balancing heavy astrophotography gear Features a nylon-tipped, tri-lobe lock knob for easy grip - even while wearing gloves in the field!