I also had 9102's (1.6 x .9 x 1.0) in both of my Angels Shadows. In looking for a replacement I ended up with the new 9550's (1.6 X.8 x 1.0) instead of the 9150 (1.9 X 1.1 x 1.0) or the 9154's. Why? Size and mounting was the biggest issue for me. The 9550's are about an 1/8!QUOT! shorter overall in mounting length but otherwise fit. The 9150 is quite a different size. Also the 9550 can be run at 6V but I am running them at 5.1 regulated. They are more than enough for a 9.5 lb two meter aileron and make an improvement over the 9102's. The centering is better and they offer instant response. My rolls show a difference. I can tell as I only changed one of my shadows and have flown both in a session with almost identical setups. The digitals are definitely worth it in my opinion.