You will need 6 buttons. Rowan used #RW5030 from Bedecked in the UK.

Finished Measurements:
Bust Circumference: 34.5(38, 42.5, 46, 50.5)“ 88(97, 108, 117, 128) cm
Finished length: 21(21.5, 22, 22.5, 23.5)” 53(54.5, 56, 57.5, 59.50 cm

Yarn used:
Rowan Felted Tweed
A. Clay 177 - 3(4, 4, 4, 5) balls
B. Watery 152 - 1 ball for all sizes
C. Granite 191 - 191, 1, 1, 2, 2) balls
D. Mineral 181 - 1 ball for all sizes
E. Carbon 159 - 2 balls for all sizes
F. Seafarer 170 - 1 ball for all sizes