D-shaped Tube

D-shaped Tube

With a smooth top, flat section and incredible lateral strength, this ingenious design prevents water ingress and it’s easy to install. Ideal for handrail in public buildings and on marine craft.

D-shaped tube, or D tube, has a distinctive ridged design which boasts tremendous lateral strength. It has a flat and secure base which is easy to apply to bulwarks, brickwork and balustrades – including glass.

  • Developed with ease of installation in mind
  • Technically and aesthetically superior to standard round tube
  • Often used as handrail due to its ergonomic design
  • Distinctive ridge creates a flat and secure base to apply to bulwarks, brickwork and balustrades
  • Clever design prevents water ingress underneath
  • Tremendous strength (49% stronger than standard round tube equivalent in robust deflection testing)
  • Joiners available for some D-shaped tube sizes, enabling easier fabrication for handrails and balustrades
  • Stainless steel tube in D-shape available in 7 existing sizes — from 34x12x1.5mm to 178x58x3mm

Originally designed to be used as handrail 

D-shaped tube is predominantly used as handrail – indeed, this is what the profile was specifically designed for. It is easy for fabricators or fitters to weld square-cut balusters directly to the underside of the tubing. Or you can attach a glazing channel to it either through welding or by attaching threaded inserts to the underside.

Easy maintenance 

The unique shape not only aids installation but it will also stop water ingress to the underside. This makes it more corrosion-resistant, as it reduces pitting and water collecting underneath. This makes D-shaped tube ideal for when used as external handrails for ramps and stairs and balustrades in public buildings, as well as yachts and cruise liners.

A great alternative to teak wood railings on boats 

For centuries, teak wood has been used aboard sea-faring craft, but teak is becoming increasingly limited in availability and increasing expensive. When made from ‘marine grade’ 316L stainless steel, the D-shaped profile makes a wonderful alternative to teak bulwark capping on larger boats and cruise liners. It has become the selection of choice for boat owners and shipbuilders alike since it requires no maintenance and will always look new. However, if a traditional teak wood-effect is desired, we can apply a special coating to the metal (this can be applied to aluminium and stainless steel tubing).

D-tube for engineering projects

Product designers and engineers have found that this geometric tube profile is an especially useful solution to house electronic components and cables. For example, we custom-make this tube in a super-slim size to be used in a piece of geotechnical equipment. If you are looking to experiment with tube shapes and sizes, speak to us about our prototypes and customised sizes.

Metals available for the D-shape profile

Most often, we make the D-shaped tube profile from stainless steel (inox) and aluminium due to the applications that it is used for, although it can be made from brass, copper and cupronickel.

Joiners available for connecting D-shaped tube

We offer a joining system for some of our most popular-sized D-shaped tubes, which enables you to produce handrail and balustrades with uncompromising, seamless joins. Find out more.


  • Railings
  • Balustrades
  • Guardrails
  • Kick rails
  • Banisters
  • Balconies
  • Metal stair nosing


D-shaped Tube Specifications

The image above shows how dimensions are detailed (for example, 34mm x 12mm x 1.5mm).Below is a table of the available stainless steel tube sizes that we have in our existing range for this shape of tube. Please note that stainless steel and aluminium 5083 oval tube profiles are sold in lengths of 5.8m (the manufacturing process reduces the standard 6m length by 0.2 metres).

Can’t see the tube sizes you need? Contact us to discuss your project requirements – we may be able to fabricate some custom-made sized tubing. Or download our sizing PDF, which contains sizing information for existing aluminium and brass tubing too, as well as all stainless steel sizes.

Upon request, we will be able to find out wall thickness tolerances from our metal suppliers. Typically the tolerance levels of wall thickness are extremely minimal and any small variations in thickness do not affect further fabrication or the end application. However, it is important to let us know if the tolerance is critical to the application before you place an order. For example, if the shaped tubing component needs to go inside another component, or if the tubing has to house a component, any variation in wall thickness could be critical. Ask us about tolerances.

D-shaped Stainless Steel Tube Sizes

Tube Size1.5mm
(Wall thickness)
(Wall thickness)
(Wall thickness)
34mm x 12mm------
50mm x 18mm------
65mm x 28mm------
99mm x 40mm------
138mm x 49mm------
178mm x 58mm---

Contact Us

For expert advice, quotes and free samples

*** We have a minimum order quantity of 1 length (usually 5.8m, depending upon metal used). Orders of 5 lengths or under incur a £50 set-up fee. We DO NOT work with mild steel.***


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