The B-series machines came out in 2004. They did some upgrades to the cab such as the side glass is removable in the b-series and the standard 226, 247,257 ect, you had to remove the glass frames to get the glass out. The door style and mounting hardware also changed. In the standard 226, 247, 257 ect the door was a flat panel glass and alot smaller than the B-series. The new style door for the B-series has alot larger viewing area out the glass and the glass is also domed out. The basic design such as the size and shape of the cabs are exactly the same, they just did some improvements to it. You can get the door kits through your CAT dealer to retrofit the larger door. If you dont have a door on it now, you have the option of converting it pretty easy. If your machine is set up for a door, this style door will not fit unless you convert it to the new style. The new style accomidates a larger opening to get in and out of the machine. It eliminates the washer fluid bottle ect.