Sorry for OTT a bit , Back to topic : Uniball Jetstream.
I never have a leak on any Uniball Jetstreams that I have. They write very nicely, better than some Zebra’s and Pilot’s ballpoint pens that I have. About the “Uniball”, I think I read somewhere that it’s a kinda hybrid between ballpoint and gel pen (???) , I don’t know , I’m not a pen-expert 
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I love ballpoint and hate gel pen.
Uniball Jetstream no failure IME.