| Although the 91 series is probably a higher quality part than the 51, the 91 has a really loose feel that I don't care for. The 96 series is better because the O-ring for the panel seal stiffens it up a bit. And the 81 series is better because of the metal shaft. But sometimes you don't have a lot of choice. Anyway, these are all perfectly good parts so use whichever you need to use. |