The core of Edmund's offerings was surplus lenses. These were single-element lenses, shipped in coin envelopes, with the "approximate" diameter and focal length stenciled on them. Reflecting their salvage and surplus origins, available diameters and focal lengths did not fall into regular progressions. Edmund published crudely printed, stapled "books" describing experiments that could be performed with their lenses, and plans for building telescopes and other optical equipment. Edmund also sold lens "kits". The 10-lens kit cost less than US$10 and included a booklet of plans for instruments which could supposedly be built with them.