Björn Borg Core Loungewear Pyjama Set. Björn Borg Core Loungewear Pyjama set is possibly the most stylish and classic pyjama set that can be found. A classic checkered pattern covers the entire pyjamas and the pyjama shirt has a stylish collar, short sleeves and buttoning at the front. The pyjama pants have a comfortable elastic waistband with drawstring and pockets on the sides. Björn Borg Core Loungewear Pyjamas is made of 100% cotton brushed flannel and works just as well to sleep in as they are stylish to wear at home.