From the Knit Rowan website:
Crochet these sweet baby bootees, a design from the Rowan archive originally featured in Classic Babies. Designed by Martin Storey using Baby Merino Silk DK, a luxury machine washable yarn designed specifically for babies (merino superwash wool and tussah silk), these irresistible bootees are fastened with one button and the colour can be varied for girls or boys.

Additional information:

2 buttons (Can use Rowan button 75333)

For Small, foot length 9cm x 1 ball
For Medium, foot length 10cm x 1 ball
For Large, foot length 11cm x 1 ball