I got the red converter because it matches, kind-of-ly, with my Sailor Night Burning pen. So far it doesn't leak and fits well. I'm happy about that! It seems to fit perfectly when the pen is screwed back into place. This is great and important because that means the converter won't accidentally slip inside the pen if it falls prevent any chance of leaking. That and the Sailor o-ring make me feel confident having this pen in my pocket.