DBOO 6 Pcs Flexible Cable Cord Grommet 25mm / 1 Inch White Desk Hole Grommet Wire Hole Cover Cable Management Wire Organizer Cable Pass Through for Office PC Desk Cable Cord Cover

These do exactly what I wanted. You must ensure that you drill the correct size hole do that they fit snugly (25mm) but once fitted you can fit one or multiple cables through them, depending on the cable thickness. I used two in a shelf for my wi fi router and ancillary items and the 6 cables I needed to feed through went on easily.

These are 20mm not 25mm.

As described, fits perfectly for a tidy finish.