Attema U50 - U40 Flush-mounted Box Spacer Ring Parametric

Attema U50 Inbouwdoos Spacer Ring - Parametric

Fully parametric spacer ring for the Attema U50 junction box (inbouwdoos), the most common electrical box in Dutch homes. Use the Customizer to adjust all dimensions to your exact needs — no CAD knowledge required.

What is it for?

When your wall finish (tiles, plaster, panels) is thicker than expected, the junction box sits too deep in the wall. This spacer ring brings the box opening flush with the wall surface, so your switch or socket plate sits flat.

Features

• Adjustable height — set the exact total height you need (2–30 mm)
• Adjustable inner diameter — open up the center for easier wiring (40–68 mm)
• Angle correction — compensate for crooked-mounted boxes by setting how many mm the gap is on one side. No more wobbly switch plates!
• Adjustable screw ears — solid material around the screw positions, always connected to the ring. Control how much material sits around the screws
• Optional lip — the original Attema spacers have a 3 mm lip that sits on the box edge. Set to 0 if you don't need it
• Screw slots — adjustable diameter and slot length, positioned at the standard 60 mm spacing

Parameters

Compatibility

Designed for the Attema U50 junction box (also sold as U50H, U50I):

• Outer diameter: 73 mm (fits the 73 mm bore)
• Screw spacing: 60 mm (standard Dutch inbouwdoos)
• Also compatible with most other Dutch single junction boxes using 60 mm screw spacing (Plieger, Hager, ABB)

Print Settings

• Material: PLA, PETG, or ASA
• Layer height: 0.2 mm
• Infill: 100% (it's a thin ring, barely uses material)
• Supports: None needed
• Orientation: Print flat (as oriented in the file)

Angle Correction

Is your junction box mounted slightly crooked? Instead of chiseling out the wall, use the angle correction feature:

1. Hold a straight edge against the wall over the box
2. Measure the gap on the wide side in mm
3. Set correction_mm to that value
4. Set correction_direction to point toward the high side (0=right, 90=top, 180=left, 270=bottom when facing the box)

The spacer will be wedge-shaped: full height on the high side, reduced on the low side.

Tips

• Start with a test print at 2 mm height to verify the fit
• The default inner diameter of 62 mm gives plenty of room for wiring while keeping the ring strong
• For extra strength around the screws, increase ear_depth_inside to 5–6 mm