Harris mod S, I think it is a 25S. The swivel is very important. Also, having that tripod open and hanging down out there steadies offhand shots FOR ME when the wind is slight. Therefore I walk with it deployed and ready to drop to my butt and shoot, but can take an offhand shot if that is all I have visibility or time for.
It does not really go low enough for prone shooting, but how often do you get a prone shot? Also when using a boulder or down tree etc it may not go low enough if you want to set up behind it. I will usually just fold it and shoot off my pack though. I'm blessed with a very forgiving collection of rifles when it comes to leaving it attached and resting the folded tripod legs on my pack.
The bipod can also straddle a fence post and let you shoot offhand.