I have an 85 K100RS and have worn out the elastic tankbag straps that mount the base to the sides of the tank. I found a BMW tankbag base on Ebay and bid on it. When it arrived and, after I mounted it, I found out it is completely different from the one I have used for years. Even though they both have K100/K75 stamped into them and mount the same, the new one is about 2/3 the length of my old one and the zippers are opposite. How many different bases did the make for the K?