The bottom of the rear seat fits fine. The upper part is not the greatest. The two main pieces fit fine, but the two slim end pieces need to have the foam trimmed down to fit the narrower B13. I have seen people that get it all to fit but I couldn't squish it all together very well. I tried pretty hard to jam all the pieces together, too. In my opinion the best solution would be to have the top half of the b13 back seat covered in black leather.
The front seats sit up a bit higher than stock seats even with NX200 seat rails. I thought it was a nice upgrade. There is a bit more support and the seats are a good bit firmer than my se-r fronts were.
Here are some shots of my front seats. I did the conversion and then sold my car. I have the leather seats for sale actually (front and rear). If I wanted to ship them, they would have been sold already.