Uni-Ball Signo RT1 UMN155-038 Gel Ink Pen 0.38mm Black Box of 10
Uni-Ball Signo RT1 UMN155-038 Gel Ink Pen 0.38mm Black Box of 10
Uni-Ball Signo RT1 UMN155-038 Gel Ink Pen 0.38mm Black Box of 10
Uni-Ball Signo RT1 UMN155-038 Gel Ink Pen 0.38mm Black Box of 10
Uni-Ball Signo RT1 UMN155-038 Gel Ink Pen 0.38mm Black Box of 10
Uni-Ball Signo RT1 UMN155-038 Gel Ink Pen 0.38mm Black Box of 10
Uni-Ball Signo RT1 UMN155-038 Gel Ink Pen 0.38mm Black Box of 10
Uni-Ball Signo RT1 UMN155-038 Gel Ink Pen 0.38mm Black Box of 10
Uni-Ball Signo RT1 UMN155-038 Gel Ink Pen 0.38mm Black Box of 10
Uni-Ball Signo RT1 UMN155-038 Gel Ink Pen 0.38mm Black Box of 10
Uni-Ball Signo RT1 UMN155-038 Gel Ink Pen 0.38mm Black Box of 10
Uni-Ball Signo RT1 UMN155-038 Gel Ink Pen 0.38mm Black Box of 10
Uni-Ball Signo RT1 UMN155-038 Gel Ink Pen 0.38mm Black Box of 10
Uni-Ball Signo RT1 UMN155-038 Gel Ink Pen 0.38mm Black Box of 10
Uni-Ball Signo RT1 UMN155-038 Gel Ink Pen 0.38mm Black Box of 10
Uniball

Uni-ball Signo RT1 UMN155-038 Retractable Gel Ink Rollerball Pen 0.38mm 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: UMUMN155-038BK

UPC: 34902778142654

MPN: UMN155-038BK

The Narrowest Width uni-ball Lists for the RT1

uni-ball describes the Signo RT1 on its own page as an "Ultra fine retractable rollerball pen for precision writing", and 0.38mm is the narrowest of the three widths its 2026 catalogue lists for the model.

The three published widths are 0.38, 0.5 and 0.7mm, and the gap between the first two is the one people actually notice. A 0.38mm line fits inside the printed boxes on a form, goes between the lines of a typed document without touching either, and puts more characters into the same width of paper. In black, that makes it the version that suits dense written work.

A narrower tip asks a little more of the paper, which is the honest trade for the extra precision. The pen is retractable, which uni-ball publishes for this model, and the ink is published as gel ink. uni-ball's site writes this width as UMN155-038, while its catalogue writes the same pen as UMN-155-38.

The wider 0.5mm version and the other colours are at gel pens. The rest of the brand is at uni-ball, other pen types at pens, and the rest of the 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
  • 0.38mm line width, published in uni-ball's 2026 product catalogue rather than on the product page
  • 0.38mm is the narrowest of the three widths uni-ball's catalogue lists for the RT1
  • uni-ball publishes the model under the group code UMN-155, this width as UMN155-038
  • Supplied as a box of 10, all one colour
  • uni-ball describes the RT1 as an ultra fine pen for precision writing
  • Writing inside the small boxes on printed forms
  • Annotating between the lines of typed documents
  • Detailed notes where paper space is limited
  • Diaries and planners with tight daily blocks
  • Technical and laboratory notebooks

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: UMN155-038

Mega Code: UMUMN155-038BK

Colour: Black

Line Width: 0.38mm (published in uni-ball's 2026 product catalogue, not on the product page)

Ink Type: Gel ink

Mechanism: Retractable

Pack: Box of 10

Barcode: 34902778142654

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 0.38mm 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.
Small spaces. Form boxes, margins, the gap between lines of print, and any notebook where you want more words in the same space. If you mostly sign things and write on ordinary copy paper, the 0.5mm version of the same pen is the easier choice.
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.
Because uni-ball writes it two ways. The uni-ball website publishes this width as UMN155-038, and uni-ball's own 2026 catalogue writes the very same pen as UMN-155-38. We have used the website spelling throughout and flagged the difference rather than picking one silently.
Ten, all black. That is the pack we hold against UMUMN155-038BK, 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.