Eyepiece Adapters
Eyepiece adapters are used to adapt from a larger focuser or star diagonal format to a smaller eyepiece format. Many telescopes are supplied with two-inch focusers or diagonals, but the majority of eyepieces will always have 1.25-inch barrels. It makes little sense to go in the other direction as a smaller 1.25-inch diagonal would vignette a larger 2-inch eyepiece. The exception to that rule is an adapter for stepping up from the obsolete 0.965-inch format so that standard 1.25-inch eyepieces may be used.