Baader Planetarium Varilock 7.5mm T-2 Extension Tube The Baader 7.5 mm T-2 Extension Tube is part of the Varilock T-2 System for setting the exact focus at intervals Determining the preload by adjusting the extension tube's millimeter scale to the desired length The Baader 7.5 mm T-2 Extension Tube incorporates both male and female T2 threads Helps to set H-alpha solar filters and image field correctors with critical focus position