These models stand less than 3" out of your focuser and the 5x takes 1 1/4" threaded filters. They are parfocal in ALL 1 1/4" diagonals and prisms. For this reason, they are highly recommended over standard Barlow for 1 1/4" diagonals and refractors such as the TeleVue-60. Note for Dobsonian/Newtonian users: When using TeleVue's Paracorr coma corrector, the 2.5x or 5x Powermate should be inserted into the Paracorr's 1-1/4" adapter (i.e., between the Paracorr and the eyepiece. For 2x and 4x 2" Powermates, first insert the Powermate into the focuser, then the Paracorr into the Powermate.