Morinaga Choco Balls is a popular Japanese candy that comes in a number of varieties. The ones that I know of are peanut, caramel, strawberry and white chocolate. I have only tried the peanut and caramel, both are made with milk chocolate coverings. Overall, they are no different than your average American chocolate candy. They come in small 1.02oz packages (they may make larger packages) and are perfectly-sized for popping in your mouth, smaller than Whoppers and larger than M&Ms. The peanut Choco Ball unlike the caramel has a wafer wrapping between the outer and inner cores, making them quite additive, this coming from a person who is not all that fond of chocolate.
Choco Balls in the 1.02oz packaging retail for around $1USD and can be found at your locate Japanese Market or online at AsianFoodGrocer.com
FoodGek 
Chocoballs have cute TV commercials too
http://www.japansugoi.com/wordpress/morinaga-chocoball-tv-commercials-in-japan/