How much tire clearance do these fender flares add?

RBS flares are designed with minimal extension to the body line, so they don't significantly increase your running tire size. Verify your current tire diameter and compare against your wheel well space before ordering if you're planning a larger tire setup.

Do I need to drill new holes to install these, or do they use the factory mounting points?

These are engineered to use existing factory attachment locations on the rear quarter panel. Drilling is not required if your factory mounting points are intact. Inspect those areas for corrosion or damage before installation.

What wheel offset and tire size are these compatible with?

Fender flare compatibility depends on your specific wheel offset and tire diameter. Measure your current setup and confirm fitment against the flare profile at the widest point before committing. This prevents rubbing at full suspension compression.