It's about 7.7cm×10cm, so a slight smaller than a regular mug.
Make of Ceramic, and (so far) it seems to be dishwasher safe.
How am I supposed to satisfy my tea lust with this?
It's a nice shade of green thankfully - I was worried it would be more yellow tha lime ^_^'
With a silhouette on the front and the logo on the back, it's plain enough to not attract too much attention, but decorated enough to prove your love for the series.
There are indeed other mugs, such as Barnaby, Ivan and Keith; but as I'm not really a huge collect-errything fan of those three, Kotetsu's enough for me.