this is a ballistic pen that only requires a spring and a rubber band to work.

the blade does not contain any holes in the model because you need to adjust it for your spring size.

you might need to sand the peices for it to work.

you also need to drilll a hole in the blade at the point wher it is alligned with the hole in the body while the spring is compressed.

you might also want to attach trhe spring inside the body with strong double sided tape.