So these are from a pocket sketchbook approximately 3"x5" and about 1/2" thick (complete with little bookmark tassel, moleskine style).
This isn't my 'primary' sketchbook, which is usually an 8 1/2"x11" hardcover or larger (now around 11"x14"), but I try to carry it everywhere, like a second wallet. Since you never know when you're gonna catch a moment.
Granted, these posts are incredibly self indulgent. I've committed to posting highlights from each sketchbook I complete, basically to give myself a bit of extra pressure to turn out good product. (whether I do or not is up to you to decide, please comment: critique is encouraged!)