Saw these on my neighbour's front yard at 304 South Kingsway (just south of Bloor). They look to be 12" x 12", but I can measure if you're interested. There are about a 16 of the ones in the right (marbled off white/light beige) and 12 of the ones on the left (marbled white). Just a couple of the darkest marbled beige ones in the middle.
Garbage day is Wednesday April 3.