Your hiking boots probably flex more.
Yes. They suck.
I put ProGrip 699 grips on all of my Ks. They come in both open ended and closed ended so be sure to get the right ones for your bike if it does/doesn't have bar ends. (Although you can cut out the center end of closed ones if you have bar ends.)
If you have OEM heated grips then you need to buy two pair because the clutch side heated grip has an added tube the same size as the throttle tube. Each pair of the ProGrips has a grip with a larger inner diameter (25mm) for the throttle side and a grip with a smaller inner diameter (22mm) for the clutch side. Therefore, if you have BMW OEM heated grips then you'll need two of the 25mm throttle side grips which is why you need to buy two pair.
They are made of a gel compound and even comfy riding barehanded. They do a good job of transferring heat if you have heated grips. They're the first thing that I install when I get a "new to me" K bike. They even come in various colors but I always get black.
If you have heated grips then be careful not to damage the HG wires when removing the old grips. The wires are wrapped around the tube and easy to damage if you are not careful.
Aerosol hairspray is good for installing them. It acts as lubricant to slide them on and then sets up. It's not as grippy as "real" motorcycle grip glue but that makes them easier to remove if you ever need to.