How to Identify Your Roller Blind Tube (Australia)

The most important step before motorising an existing roller blind is identifying the tube. The outside diameter gives you a clue, but the internal profile is what confirms whether a motor, crown and drive will actually fit. Two tubes can look almost identical from the outside and still need completely different motor adaptors.

Why the tube matters more than the motor brand

A tubular blind motor sits inside the roller tube. The crown supports and tracks the motor inside the tube, while the drive transfers the motor's rotation into the tube. If those parts do not match the internal profile, the motor can turn without driving the blind correctly. That is why choosing a motor before identifying the tube often leads to the wrong parts.

Step 1: Remove the blind and expose the tube end

Take the roller blind down from its brackets and remove the non-chain end, or idler, so you can clearly see the aluminium tube profile. A straight-on photo of the open end is far more useful than a photo of the outside of the blind.

Step 2: Measure the outside diameter

Measure straight across the outside of the aluminium tube, not across the fabric roll. Common Australian profiles include S45 Light at about 43mm, S45 Standard at about 44mm, S45 Heavy Duty at about 49mm, S40 at about 39.4mm, 38mm Standard at about 38.1mm, S60 at 60mm, HD50 at about 50.8mm, S35 around 33–34mm and L45 at 45mm. The measurement narrows the field, but it is not enough on its own.

Step 3: Match the internal profile

Compare the shape inside your tube with a known profile. Pay attention to splines, slots, ribs and wall thickness. For example, L45 can measure a true 45mm but is not the same internally as an Acmeda S45, so standard S45 crown and drive adaptors are not interchangeable.

The common tube families we identify

• Acmeda S45 Light, Standard and Heavy Duty — common modern Australian roller blind profiles.

• S40 T-Spline — an older Acmeda profile still found in many existing installations.

• 38mm Standard — a compact thick-wall tube used on many smaller locally made blinds.

• S60 and HD50 — heavy-duty tube systems used for wider or higher-load blinds.

• S35 and L45 — older or less common profiles that need more careful compatibility checking.

What if your tube does not match?

Do not force a motor into a tube just because the diameter seems close. Thin-wall retail tubes, small 25–28mm tubes and smooth 32–34mm tubes with no usable internal profile often need to be replaced before reliable motorisation. You can normally keep the existing blind fabric and upgrade the tube and hardware instead.

The fastest next step is to use our Identify Your Tube guide. It shows the actual tube profiles and then sends you to the motors confirmed to fit the tube you have.

Frequently asked questions

Can I identify a roller blind tube without taking the blind down?

Sometimes you can estimate the tube family from the outside diameter, but a confident motor match normally requires seeing the open end and internal profile.

Does a 45mm measurement mean I have an S45?

No. Several tubes sit around the 45mm size. The internal shape is the deciding factor, especially when distinguishing Acmeda S45 profiles from L45 and other round tubes.

Once you know the tube, the rest becomes much easier: confirm the compatible motor, select the correct crown and drive, then retrofit the blind. For the full process, see our DIY guide to motorising existing roller blinds.