Stella McCartney Kids Trousers. Grey tracksuit trousers by Stella McCartney Kids. Made in soft, fleece-lined organic cotton jersey, they feature an all-over 'Roll Up' circus print. They have side pockets and an elasticated, drawstring waistband.and The ankle cuffs and waistband are ribbed. The fit can be quite small, so Stella McCartney advises you to choose a size up if you want room to grow. Size - 18 months Ref: SB5