Celestron 80mm Guidescope Package with 125mm Rings and 80mm Guidescope with Extension Tube Complete package includes 125mm rings and 80mm Refractor Guidescope 600 mm (23.62 in) Focal Length with 7.5 Focal Ratio Compatible with Celestron NexGuide Autoguider Includes Extension Tube to help reach focus without having to use a diagonal M42 thread on extension tube allows you to slide NexGuide autoguider barrel into extension tube or thread guider directly onto extension tube