These Vortex Push-On Objective Caps are originally supplied with the Fury, Razor, and Viper binoculars which have 42mm objective lenses, and are offered here as a replacement for a lost or damaged cap.
They'll also fit many other binoculars as an optional upgrade. It is difficult to say which tethered caps will fit which binocular, since it is such a finicky application which is often dependent upon the objective lens barrel's edge design. But if these caps have been recommended as an accessory to a binocular, you can be assured that we have tested the fit here at B&H. Consider the stated 50mm outer barrel diameter estimate, common to many 40-42mm objective binoculars, as a guideline.