Guide to Ballpoint Pen Refills - The Pen Refill Guide
Standard: C1. Length: 117.5 mm (4.625″) The C1 is a Cross Style ballpoint pen refill. The official ISO standard length is 117.4mm, but most of these refills actually measure out to 117.5mm, or exactly 4.625″. This refill is a long metal or plastic tube with a threaded, knurled knob on the back.