I was changing batteries in the wireless mics at work the other day and took just a minute to be thankful for something that Sennheiser has been doing for a while now. (I don't know if other manufacturers do this too and also we receive no compensation from anyone for mentioning brand names)
Since wireless mic designs that use AA batteries have hit the market doing a quick change has gotten a lot easier. Back in the 9v days you had to memorize which way the battery went and if you had different models you had to remember which was which. Otherwise swapping one out at thirty seconds to curtain in the dark back stage became a real panic situation. At least with double As you can usually feel for the spring on each side and get them in there the right way.
With the addition of one tiny strip of metal Sennheiser has done away with this completely. Both batteries go the same direction and the positive side is always down. I can swap a pair out with one hand in the dark and hand a mic back to a performer in a flash. So my thanks go out to product engineers who notice little things like that and take the time to come up with a better way. Even the littlest things can make your day go better on a gig.