This product is specially designed for use with a Moleskine (13x21 cm Hardcover) sketchbook. (Softcover booklets have not been tested.) This shell takes a standard BICcristal ballpoint filling. The pen is delivered in three pieces.
The Cap-on-book function will keep the cap of your pen on the booklet even when it is open. The extra wall slides between the side of the expandable back pocket.
Assembling is easy. Put the smal piece on the rectangular end of the piece with the round hole. If it doesn't stay in place you can use a little bit of glue (make sure the glue you use doesn't react with the 3dprint). The last thing to do is te get a BICcristal filling, and insert it into the round hole. The third piece is the cap of the pen.