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Made to order

The New Boss Design Sia Eco Friendly Office chair

Sia is the latest task chair from Boss Design and is heavily focused not on on ergonomic comfort but also the environment.


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£345.80 inc. VAT

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Available as made to order

Made to order in 4 Weeks

Product Details

100mm lumbar height adjustment

65mm seat depth adjustment

120mm seat height adjustment

Intuitive weight-balance mechanism with additional tension adjustment

 Black Nylon five-star base with black castors as standard

Height adjustable arms

As standard, the Sia lumbar pad will be colour matched to the frame colour chosen (Black, Copper Brown, Reed Green and Oyster White).


During the Sia chairs design process sustainability was key.

With the Sia Chair Boss managed to drive the plastic used in the structural parts of the chair down to just 20%. The remaining 80% is recycled plastic.

Sia Eco friendly chair uses fewer components than most task chairs and is assembled without the use of glue.

This makes replacing damaged parts more feasible extending Sia’s longevity while also making it easier to separate and reuse or recycle components at the end of its life cycle.

Sizing & Warranty Information

  • Assembly
    Fully Assembled
  • Warranty
    5 Years
  • Seat Height Range
    400mm - 510mm
  • Maximum User Weight
  • Country of Origin



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Delivery & Returns Information


Our standard delivery is FREE of CHARGE to the UK mainland. Items FROM STOCK we aim to Deliver in 3-5 working days  (unless otherwise stated) MON- FRI  8AM TO 6PM .

* Excludes the Scottish highlands which is chargeable.

If the item is ( Made to Order) you can find the lead time under the Add to Basket Button (these are as accurate as possible)

Products showing PRE ORDER are items we have coming back in to stock and the dates are on the product pages. When you buy a pre order item it is reserved and when it arrives with us we ship it on to you please allow 3 working days after date shown for delivery.

We also ship to NI, ROI and the Channel islands also Mainland Europe.

For more information, please visit our dedicated Delivery Information page.

Easy Returns

All items listed as in stock can be returned or exchanged easily. The item must be in the original packaging and in New Condition and unused! You have 14 days from the date the item was received. We can arrange the return for you.

Please advise of the order No, address and contact details in the email sent to logistics@officechairsuk.co.uk.

For more information, please visit our dedicated Returns, Exchange & Refunds page.

Back view of the Sia lumbar support

Maximum Comfort & Support

Ergonomic Comfort

Our design team worked closely with leading ergonomist Levent Çaglar at FIRA while developing Sia, resulting in a task chair providing optimum comfort and support.

With the right amount of flex and twist in the back section, Sia moulds to the human form, providing lumbar support without restricting movement.

Its generous high back, a lumbar pad that is adjustable across a 100mm range, and multi-adjustable armrests make Sia customisable to a wide variety of body shapes and sizes.

This is a chair built for maximum comfort, concentration and focus, facilitating wellbeing and productivity in the workplace.