Navy And White Cotton-flannel Pyjama Trousers, Elasticated Drawstring Waist, Four Pockets, Buttoned Fly, 100% Cotton, Machine Wash Or Dry Clean. Derek Rose's checked cotton-flannel pyjama trousers are timeless. Worn with a crew-neck tee and slippers, their relaxed fit and soft hand is sure to keep you comfortable on your downtime.