For embedding in the ceiling / walls (cutting holes in the material), the model has an auxiliary geometry for applying CoronaDistance / VrayDistanceTex (settings and parameters are attached in the archive).

The dimensions can be changed as necessary, the manufacturer makes them to order (maximum and minimum dimensions are described below).
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1. Linear.
Slit linear diffusers of flush mounting frameless invisible RED ONION.
The recommended maximum size is 2500 mm. The recommended minimum size is 300 mm. The fixed size of the slots is 30 mm. The number of slots is from 1 to 6. With visible slats and hidden under the plaster.

2. With a slit around the perimeter (square, can be rectangular).
Designer ventilation grilles RED ONION-SIR.
It is used as a supply or exhaust diffuser. The width of the gap is 10, 15, 20 mm. The minimum dimensions of the front panel are 100 mm vertically and horizontally. The maximum dimensions of the front panel are 300 mm vertically and 1000 mm horizontally. It can be finished or with a finished metal panel.

3. Perforated round.
The diffuser is a round supply and exhaust air with holes and RED-VAZ magnets.
Possible standard sizes - 100, 125, 150, 160, 200, 250 mm.

4. Square and round protruding from the ceiling/wall plane.
RED-DIZ diffuser is a designer supply and exhaust air diffuser.
Minimalistic design. Standard sizes are 100, 125, 160, 200 mm.

5. Slit diffuser with AVIO microswitches.
The number of nozzle rows is single row / double row. Standard sizes – 500, 1000, 1200, 1500, 2000 mm. The nozzle colors are black, white, gray, blue, light green, red. The coating of the main panel can be smooth or rough.

From another manufacturer:

6. Annular slit diffuser (for stretch ceiling and drywall).
Magnetic ventilation grate Ø125 (150)* ECLIPSE

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! The renderers are made in Corona, the conversion of materials to Vray is done using Vray-converter !
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For Corona render, it is recommended to install a version not lower than 1.5, since the glossiness of materials is configured with PBR in mind

Who works in a V-Ray version lower than 3.1 be careful, in the materials in the BRDF section there is a Microfaset GTR ( GGX ), if your version is older than 3.1, then the BRDF field will be empty. Choose Blinn, Phong or Ward – which is preferable for you