Those who enjoy natural (that is, non-hydrogenated) peanut butter know that a new jar will present itself with the peanut oil mostly separated from the ground peanuts. Getting the two mixed together, with a knife or chopsticks, can be a messy affair, with peanut oil slopping over the side of the jar. The solution is Witmer's peanut butter mixer. This item is comprised of a metal screw-on lid that fits standard 16 oz. jars (e.g., Adams, Laura Scudder, Smuckers), and an arc-shaped stirring rod-and-handle that fits through a small hole in the lid. You simply screw the lid onto your new jar, insert the stirring rod through the hole and turn the handle a few times. The result is not always completely mixed (especially for crunchy peanut butters), but it's sufficiently started to finish up with a knife - about the same work as re-stirring after you've let a jar sit for a day or two. Clean up is a breeze: a rubber gasket on the lid's hole cleans the stirring rod as it's removed from the jar, and a polypropylene insert inside the lid pops out for easy washing. Amazon lists only the standard model (the #100) for 16 oz. jars that are 4.75 inches high and have a 3 inch diameter lid. Additional models for reduced fat, small mouth, 26 oz., 36 oz., 60 oz., and no salt jars are also available from the manufacturer. Replacement parts can also be purchased separately. [ 2008 hyperbolium dot com]

I tried every utensil to mix natural peanut butter and it was always a mess. Hard to blend well, oil dripping down the sides, and a lump of "clay" at the bottom from insufficient mixing that I couldn't even eat.
This apparatus is genius.

Couldn't be any easier to use. I was trying to stir my almond/peanut butter with a knife and didn't realize how much was never really mixed. Now from top to bottom it is fully mixed and once you pull the handle out it is virtually clean....no mess. Love it and would definitely recommend it.

This thing is absolutely amazing! I had to go through the company website to get the right size for the jars we use, but I could not be happier. With 5 kids, we go through a lot of peanut butter and I used to hate having to open a new jar. Silly as it sounds, I now look forward to it because this little doozie makes it a breeze! Definite must-have!

The lids of peanut butter jars are not necessarily standard. The lid with the product only fits some jars on the market. If the lid fits the product works fine, it the lid doesn't its useless.