The dual-speed Crayford focuser features a focus control with 1:1 and 10:1 speed ratios allowing superbly smooth and precise focusing at all magnifications. The focuser attaches to the telescope via four holes positioned in each corner of the mounting plate. The overall length of the focuser (including the 1.25" to 2" eyepiece adapter), measuring from the edge of the mounting flange is 2 inches(50mm). Racked out, the total focuser tube extension(again minus the eyepiece adapter) is 4.5 inches (115mm). The mounting pedestal measures 3.5 x 4.5 inches (90 x 115mm) and is 1/2 inch (13mm) deep at it's thickest point. The focuser is fully (360 degrees)rotatable when fitted to the telescope. The focuser has adjustable tension and stiffness making it ideal for carrying heavier eyepieces and cameras. And allows the focus point to be locked by actually disengaging the focus control knob via a thumb knob. This is a beautifully engineered focuser and it functions every bit as well as it looks! There is absolutely no backlash and the adjustment can be super light-touch or stiff as you need it - but always with an ultra smooth feel.