I've recently bought some "Cross" style refills from my local OfficeMax. Many of my clients are government employees, and they use blue ink for originals. The blue ink refills would not fully extend in the bullet pens I had made. They have a slightly larger banding behind the point. A customer allerted me to the problem, which was an easy fix, but it's a good reminder to test new or different refill brands before letting them out into the wild.