CBI makes them flat. I just installed mine. I'm not sure how I feel about these coming from the OEM side steps. I also wanted a 20 degree slider, but couldn't figure out how to use the Westcott website. Now that I have these CBIs I'm realizing that-
1. Sliders are a bit smaller than steps as a step surface. Adding 20 degrees of tilt might make it a bit too small if someone other than you is going to use it. It's really easy to miss them when getting out of the car.
2. The 20 degrees won't make any noticeable difference on rocks. They have tubes all around. If anything it'll let rocks get a little closer to the body. My main concern with sliders is the way they connect to the frame and how likely those parts will catch on rocks. Don't know about others, but after installing the CBI sliders, I noticed they're tucked in a tiny bit higher than I feared, so overall I think they're good.
3. 20 degrees might look better. There's a bit of a space between the slider and the body (which the OEM steps covered nicely), making the sliders look a bit after-markety. They're very well made and finished, and that space is probably a good thing for when they get real big impacts. Also lets me stick my foot in better.
Anyway, I suggest you get good pictures or see in person whatever slider you're getting, unless this is all about rocks and not about looks / comfort.