The 2" Deluxe eyepiece clamp changes the 2" thread of a Schmidt-Cassegrain telescope into a 2" receptacle. It consists of two parts - the precise 2" eyepiece clamp with two large knurled locking screws and built-in bronze compression ring, and a factory-mounted inner thread ring that reduces the native telescope sided M58 inner thread to a 2" inner thread.
With this adapter, you have a fully illuminated field. Star diagonals with SC connection of have a narrow adapter causing loss of light. With this adapter and a 2" diagonal mirror, you can use all the aperture you paid for. Additionally, you can take full advantage of the wide 2" range of accessories such as focal reducers and field flatteners, 2" star diagonals and eyepieces.