Uni-Ball Signo RT1 Gel Ink Pen 0.5mm Black Box of 10
Uni-Ball Signo RT1 Gel Ink Pen 0.5mm Black Box of 10
Uni-Ball Signo RT1 Gel Ink Pen 0.5mm Black Box of 10
Uni-Ball Signo RT1 Gel Ink Pen 0.5mm Black Box of 10
Uni-Ball Signo RT1 Gel Ink Pen 0.5mm Black Box of 10
Uni-Ball Signo RT1 Gel Ink Pen 0.5mm Black Box of 10
Uni-Ball Signo RT1 Gel Ink Pen 0.5mm Black Box of 10
Uni-Ball Signo RT1 Gel Ink Pen 0.5mm Black Box of 10
Uni-Ball Signo RT1 Gel Ink Pen 0.5mm Black Box of 10
Uni-Ball Signo RT1 Gel Ink Pen 0.5mm Black Box of 10
Uni-Ball Signo RT1 Gel Ink Pen 0.5mm Black Box of 10
Uni-Ball Signo RT1 Gel Ink Pen 0.5mm Black Box of 10
Uni-Ball Signo RT1 Gel Ink Pen 0.5mm Black Box of 10
Uni-Ball Signo RT1 Gel Ink Pen 0.5mm Black Box of 10
Uni-Ball Signo RT1 Gel Ink Pen 0.5mm Black Box of 10
Uniball

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

$22.53
$22.53
RRP $23.87
Or 4 payments of $5.63 with
Add items to a quote for bulk pricing, approvals, or purchase orders.

SKU: UMUMN155-05BK

UPC: 34902778142814

MPN: UMN155-05BK

A 0.5mm Line for Everyday Office Writing

uni-ball publishes the Signo RT1 as an ultra fine retractable rollerball pen for precision writing, and its 2026 catalogue puts this version at a 0.5mm line, in black.

Black at 0.5mm is the width a desk settles on without having to think about it. Narrow enough that a signature block or a tightly printed form stays legible, wide enough that a full page of handwriting still reads easily at arm's length. uni-ball describes the ink on its own product page as gel ink, and calls this generation new improved gel ink, which is uni-ball's wording rather than ours.

Retractable matters more than it sounds for a pen that lives in a shirt pocket or the back of a drawer. No cap to lose, and none to leave off. uni-ball lists the pen under the group code UMN-155 and publishes this width as UMN155-05, so a reorder can be matched on a code instead of a colour name.

The 0.38mm version of the same pen, and the other colours, sit at gel pens. The rest of the brand is at uni-ball, other pen types at pens, and the wider desk at writing supplies.

Often ordered together

  • Retractable, as published by uni-ball for the Signo RT1
  • Gel ink, described on uni-ball's own page as new improved gel ink
  • 0.5mm line width, published in uni-ball's 2026 product catalogue rather than on the product page
  • Black ink, the default choice for forms and signing
  • uni-ball publishes the model under the group code UMN-155, this width as UMN155-05
  • Supplied as a box of 10, all one colour
  • Signing forms, dockets and delivery paperwork
  • Daily note-taking in meetings and on site
  • Filling printed forms where the boxes are small
  • Desk and reception pens kept as a shared box
  • Staff starter kits and stationery cupboard stock

Shipping

Shipping is kept simple with flat rates for selected areas and free shipping where applicable. Large, bulky, rural or out-of-area orders may require additional freight, and our team will contact you if this applies. For a more specific estimate, simply add this product to a quote or visit our shipping page.

Delivery Times

Melbourne, Sydney, Brisbane, Adelaide — 1 to 3 business days
Perth — 1 to 5 business days
Regional & Outer Areas — 3 to 7 business days

Returns

If you have questions about returns, please contact us or visit our returns page for full details.

Specifications

Brand: uni-ball

Range: Signo RT1

Model Group: UMN-155

Manufacturer Code: UMN155-05

Mega Code: UMUMN155-05BK

Colour: Black

Line Width: 0.5mm (published in uni-ball's 2026 product catalogue, not on the product page)

Ink Type: Gel ink

Mechanism: Retractable

Pack: Box of 10

Barcode: 34902778142814

Refill Code: Not published by the manufacturer

Country Of Origin: Not published by the manufacturer

Primary Distribution Centre

Factory 5, 12 Greenway Drive
Tweed Heads South NSW 2486

ABN 18 634 002 609

Get directionsContact us

FAQs

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.
The 0.5mm lays a slightly wider line, which is the safer default for general office writing and for paper that is not especially smooth. Choose the 0.38mm when you are writing into small printed boxes or annotating between lines of type.
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 black. That is the pack we hold against UMUMN155-05BK, read from this product's own record rather than assumed from the range.

Shipping & Delivery

Delivery time depends on your location, the size of your order, and the shipping option selected at checkout. For in-stock items, standard metro delivery in QLD, NSW and VIC is usually 1 to 7 business days. South Australia, Tasmania, Western Australia and the Northern Territory are generally 3 to 12 business days. Express delivery for eligible parcels under 3kg is usually 1 to 4 business days in QLD, NSW, ACT and VIC. Delivery estimates apply to in-stock items only and may vary due to carrier conditions or delays.

If you need to make a change to your order, please contact our team as soon as possible. Once an order has been processed or dispatched, changes may no longer be possible. You can contact us through our Contact Us page for assistance.

Mega Office Supplies ships orders Australia wide and occasionally internationally. The best avenue would be to contact us so we can customise a specific quote for you. Please note that associated international duties, taxes and levies will be the responsibility of the customer.

Returns, Refunds & Replacements

Mega Office Supplies accepts change-of-mind returns for unopened and unused products within 14 days from the invoice date, provided the item is returned in its original packaging and in resalable condition. Original shipping costs are not refundable, return shipping is the customer’s responsibility, and a restocking fee may apply depending on the product type and supplier. Some items, including electronics, assembled or installed furniture, food, beverages, medicines, custom-made products, and certain bulk or special-order items, are not eligible for return unless required under Australian Consumer Law.

If your order arrives faulty, damaged, or incorrect, please contact Mega Office Supplies as soon as possible. Where required under Australian Consumer Law, a repair, replacement, or refund will be offered. In these cases, Mega Office Supplies will cover reasonable return shipping costs, and photographic evidence may be requested to help process the claim. Items should be reported within a reasonable timeframe after delivery.