 Textile measurements are taken at a standard temperature and humidity, because fibers can absorb moisture from the air.The actual length of the yarn contained in a ball or skein can vary due to the inherent heaviness of the fibre and the thickness of the strand; for instance, a 50 g skein of lace weight mohair may contain several hundred metres, while a 50 g skein of bulky wool may contain only 60 metres.There are several thicknesses of craft yarn, also referred to as weight.