N40. 2" (50.8mm) diameter X 0.125" (3.175mm) thick, magnetized through the thickness.
Note: This magnet is in my "Serious Pain" category. Yes, that means what it says - if you get your fingers caught between 2 of these you can get serious blood blisters and it will definitely hurt. Of course you can get some pain relief by quickly holding one of the poles on the injured area.
Although many pieces are shown here, price is per piece.