This pattern has lengths in inches only. Sizes are XS, S, M, L & XL. The sweater does not weigh 900g, but you have to buy at least 1 ball of the contrast colours, sometimes 2. The actual yarn requirement is:
Rowan Wool Cotton: 500(550, 600, 650, 700)g Colour A; 100g Colours C, D; 50g Colours B, E, F & G