Uni-ball Signo Bit UM-201 Gel Ink Pen Refill - 0.18 mm - Red

YES! XD This refill fits in the 0.28mm red pen body. I bought the 0.28mm red pen and this 0.18mm red refill because the 0.18mm red pen was out of stock (is it out of stock forever? I dunno, but it's a fantastically smooth tiny-writing pen, maybe even better than the black 0.18mm, so buy them while you still can!)