These funky watches are "geek chic", math inspired apparel. Great gift for students of all ages or for anyone who loves math: numbers are equations to figure out. Choose "Chalk" or "Graph." Dimensions: black chalkboard: .875" diameter x 9.25" long strap; clear graph paper: .625" diameter x 8.75" long strap. This is the watch version of the popular Chalk Board and Graph Paper Clocks (see below).