By pressing the yellow plunger at the end of the pencil, the selected lead will drop out to it's maximum length, and then is held by a retaining clip at the end of the lead. The length of lead can be adjusted as in most drafting pencils by holding the plunger down and pushing the lead to the desired length. Leads can be removed by rotating the plunger index to be in line with the clip. Pushing the plunger will then release the old lead and a new one can be inserted. The model number for this little gem is PH158.
Some models come with a blue clip instead of an orange one.
An instruction sheet comes with the pencil. Was discontinued a few years ago. It writes blue, black, red and green inks. Each cartridge is refillable and retractable. There are four colored push tabs at the top of the pen.