This standard size bobble hat is hand knitted in the round (meaning no seam!) with an attached bobble using the same wool. The acrylic wool is self patterned with yellow, red, orange, purple and some green tinted wool.
 
The bottom edge circumfence is 57 cm. It can stretch a little  bit, meaning it can fit a good number of head sizes.
Length from edge to bobble is 19cm.
 
However, as it's acrylic and not proper warm wool, it should not be worn when it's really cold. I wear one myself and noticed it recently.