I built my kit around the telescopes I have. Mostly useful focal lengths for my 12". Some eyepices are used for planetary and seeing as deep as possible,some are for the whole space-walk experience, and some are novelty or grab-and-go type of setup. Admittedly some I haven't used for years. They just sit in my case and I lend them out to people who still use generic plossls that came with their scopes.