lady in a grey core warmer, the Koji Fine
grey core warmer, the Koji Fine
black core warmer, the Koji Fine
2 black core warmers overlaid to show the difference in size between S/M and L/XL
a black and grey core warmer, Koji Fine in M size
a close up of a black core warmer, the Koji Fine, to show the thickness which is 3mm
lady wearing a grey core warmer,the Koji Fine and pulling it out to show the stretch

Koji Fine core warmer

Regular price £14.00 Sale price£10.00 Save £4.00
Tax included. Shipping calculated at checkout.

  • In stock, ready to ship
  • Inventory on the way

The Koji Fine is a thin but snug, stretchy, waist-warming band. Pull this on after a cold swim and it will add an extra insulating layer to your core to help heat you through. Lots of warm layers are the best way to heat up slowly after chilly dips and this makes a great addition to the layering process.

It's so easy to step into, so cold, fumbling hands are not a problem and it can also double up as a modesty cover if you pull it over your boobs when changing.

Wear it next to your skin for a soft and warm base layer.

The Koji Fine is our thinnest Koji at 3mm thick and yet it still provides great warmth without being bulky. Choose this Koji if you want to forget you are wearing it or are trying to keep a sleeker look in your post-swim layering process. Also great for everyday wear in winter. 

Get cosy in a Koji! You'll end up wearing it all day - not just post swim!

Available in black and grey

Size Guide

The below is a guide but as the Koji Fine is a stretchy garment there is the possibility to size up or down. Size down for a snugger fit and size up for extra stretch (possibly to cover boobs when changing)


Waist in cm

Waist in inches

UK dress size












Delivery & Postage Charges

The lead time between receipt of your order and dispatch is normally 24 hours, with a maximum of 72 hours. The brand will inform the Operator (The Outdoor Swimmer Shop) within 24 hours if they are unable to fulfil any orders received and we will contact you.

Shipping Charges to the Customer:


UK £3.99

EU £7.99

Rest of the World £14.99

Magazine (Only):

UK £1.00

EU £2.50

Rest of the World £3.50

We will only refund any shipping costs, including the cost of returning your goods, if we shipped an incorrect product or the product is found to have a genuine fault or is otherwise imperfect. Unsuitable wear or intentional damage will not be regarded as a fault. If you are claiming that your purchase was faulty, we will inspect your returned item(s) and let you know within 10 days whether we agree or if we regard the product as not faulty. 

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