Gravity sensor switch ?

Our electric Pepper Grinder with Gravity sensor switch, you won’t need to press a button, Simply flipped the grinder and you will have fresh ground spices.

Do they make noise when grinding?

Of course they make noise while grinding. But it is not loud or annoying in any way. These are the best grinders ever. Way better than the pair I bought at Amazon several years ago that have a push button on top. I quickly got used to having a bit more salt or pepper come out as soon as I tip them towards my food due to the little bit left over from tilting the shakers upright after the last use while they still grind a little.

When trying to take bottom off to put more salt in, it will not come off and the metal ring simply slid off, is there a fix for this?

Same. right out of the box I put batteries in and salt and it worked fine but the other one I was not able to get the bottom off to put pepper in so I went back to the one with the salt to see if this was a righty tidy lefty, Lucy, or was it backwards and now I’m finding I can’t get the salt bottom off either. i’ve also given this to my husband to try to loosen and he couldn’t get it off either.

How many ounces of product does it fit?

Instructions say fill container about 80% of product. Container looks to be about 8 oz. So I would estimate about 6oz. This is a gift so I’ve not used.