I needed some grommets for a control board project I'm working on so I ordered a 10 pack.
Installation was easy, I had 1" grommets so I drilled 1" holes. When drilling your hole, be sure to keep your bit/hole saw straight. If you angle it, the hole will be loose. Some black duct tape wrapped around the "plug" part of the grommet will fix that problem.
Painting - They can be painted, if they're going to get banged, bumped or have wires moving on them, like on top of a desk, you should prime them first. If you paint them without primer, even using paint made for plastic, the paint can/will chip off.
Price - I bought the 10 pack (only needed 6) so they came out to $1 per grommet, a little pricey for what they are. If you have a larger project or want some spares, the 20 pack is only $.84 per grommet, saves a little bit of money.