Schneider&reg; Topball 850 Green Rollerball Refills-box of 10 you are buying ONE box of 10 Topball 850 green medium refills aka "universal rollerball refill";fits most capped rollerball pens ink line: 0.5 mm green Buy with confidence from an authorized USA Schneider Retailer. Manufacturers will only honor warranties/replacements on products purchased from an autorized dealer. Buy authorized....don't get burned