The Tri-knob with LOCK knob option adds the shaft lock system to the coarse side. The shaft lock option uses a unique mini brass compression ring clamp sub system that allows the user to lock the shaft with out deflecting the drawtube. This type of focus lock is much better then the old "thumb screw against the draw tube" style that would shift the image when pressed against the draw tube. The shaft lock ability along with the 6 lb heavy-duty reduction unit make this option ideal for heavy demanding loads for both visual and imaging requirements.
This focuser fits direct on the Celstron C11 and 14
it fits also on the special EdgeHD reducers from Celestron