This Deluxe kit includes the parts you will need for both "Prime Focus" and Variable "Eyepiece Projection" The "Variable" feature lets you adjust the adapter length to vary the magnification (thus image size) for perfect framing of your shots. Fits telescopes with a standard 1.25" eyepiece port. The adapter can hold eyepieces up to 42mm in upper body diameter. It also features a laser engraved extension scale for recordability and repeatability as well as a large machined grip ring.for a sure grip in even the worst dew conditions. CNC machined of aluminum with a durable black anodized finish. The 1.25" barrel is threaded to accept standard 1.25" Eyepiece Filters. Reflectors typically require a barlow lens to be placed between the adapter and focuser to extend the focus point. Refractors typically require you to replace the diagonal with a slightly shorter extension tube to reach focus. this is true of any adapter. most SCTs and MAKs wont require anything else Prime Focus Application: typically used for imaging nebulae; galaxies and other large (but dim) deep sky objects Eyepiece Projection & Variable Eyepiece Projection Eyepiece Projection is typically used for Terrestrial, Lunar & Planetary imaging and any time higher magnification is needed to bring out detail Eyepiece Diameter: Compatible maximum eyepiece diameter is 42 mm.It can handle larger eyepieces (to 42mm Max Dia), has a handy laser engraved Extension Scale and a machined Grip Ring