Tested on all types of pencils I had. Worked great for holding Prismacolor Premiere, Prismacolor Verithin (Hex Cylinder), Faber Castell Ecopencils (Hex Cylinder), CastleArts, Sanford, Deli/StarJoy, some old Dixon Thinex and even Crayolas. Everything worked great in the mounts. The only thing I didn't like was the lack of a pocket to store it when not in use. They fit perfectly in aftermarket pencil cases, but will stretch the elastic of pencil cases that use separate loops for each pen. A caseโฆ