You will need 2 buttons. Sirdar used their button # B5611-0785

Finished measurements:
Circumference at chest: 16.5( 18, 19.75, 20.5, 21.25, 22)“ 42(46, 50, 52, 54, 56) cn
Width at waist: 18(19.75, 21.75, 22, 22.75, 23.75)” 46(50, 55, 56, 58, 60) cm
Finished length - hem to shoulders: 15.5( 18, 21, 22.75, 24.75, 26.5)“ 39(46, 53, 58,63, 67)cm

Yarn used:
Sirdar Snuggly Cashmere Merino DK
Shade 467 Silver - 2(3, 4, 4, 4, 5) balls