Rollerball Pen Refill Case

My daily carry rollerball pen's cartridge is due to be replaced soon and I didn't want to carry the refill loose in my bag for fear of damaging it/exploding it all over the inside of my bag. Should fit any refill with a 6.3 mm diameter (0.25 inch) and a LOA ~112 mm (4.4 inch), including a Pilot G2 refill. Friction should keep the cap attached, but if not there is a provision in the bottom of the case for a small spring to keep it shut. The cap was printed without support, open end facing up while the body was printed with the opening against the bed to support the locking lugs.