The 2 knurled screws hold your accessories in a very tight grip and make the clamping mechanism extremely easy to operate in the cold or whilst wearing gloves.

With this adapter, you have a full, bright field of view, some star diagonals, with SCT connection of have a narrow field that causes loss of light, with this adapter and a 2" diagonal mirror, you can use all the aperture to the fullest.
In addition, you can use alongside a full 2" accessory range, including:

•  2" star diagonals
•  Focal reducers and field flatteners
• 2" eyepieces and adaptions