These are our popular 1" diameter x 1/2" thick neodymium disc magnet with a protective thermoplastic coating. This coating makes these magnets very water resistant and virtually indestructible. They can be slammed together with little threat of damage to the magnets. The rubber-like coating is grippy, which is great when sliding is a problem, like we describe in our Leverage & Friction article.
The dimensions of these magnets are the outer dimensions of the thermoplastic coating.