Diopter Lens for Peep Sights?

[Cow Tag]

Hunters, have any of you tried the available diopter lens that can be inserted into a peep sight? I am needing some help in gaining information about these diopter lens. Anyone ever tried them on their muzzleloader rifles? I know the company from which to order these lens plus the fixtures necessary to mount them on the sight, just wanted some honest opinions about these lens. CowTag