This 5.6mm insert converts any 5.6mm lead pencil to a pen ! The insert holds a standard mini pen refill so the insert can be refilled indefinitely and with optional mini refill. Use the insert by simply popping out the lead of your 5.6mm sketch or shop pencil and replacing it with this insert. Each insert includes a black ink mini pen refill. The refill easily unscrews from the insert for replacement.