Uni-ball Signo RT1 UMN155-05 Retractable Gel Ink Rollerball Pen 0.5mm Green Box of 10

uni-ball's product page for the Signo RT1 does not publish a tip size. The 0.5mm figure is published in uni-ball's 2026 product catalogue, which lists the model in three widths. We have attributed it to the catalogue rather than the page so you can see which source it rests on.

uni-ball publishes no refill code for the Signo RT1, so we are not going to name one. Other Signo models take their own specific refills and guessing across models is how the wrong cartridge gets ordered. Ask us and we will chase the code through the supplier.

Because two colours run out of meaning quickly. Once black is the original and red is the correction, a third colour is the only way to show a second person has been over the page. Green is the usual choice for that, and for anything marked as passed.

Retractable. uni-ball states that on its own product page for this model, which is why we are comfortable publishing it. There is no cap.

uni-ball is not consistent about it. The uni-ball website publishes this width as UMN155-05, while uni-ball's 2026 catalogue uses a different pattern for the family, writing the finer 0.38mm pen as UMN-155-38. The two sources do not spell the range the same way, so we have used the website spelling and flagged it rather than picking one silently.

Ten, all green. That is the pack we hold against UMUMN155-05GN, read from this product's own record rather than assumed from the range.

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