This is a Fil Au Chinois polycotton thread for leather work. It is not a mix of polyester and cotton. It is what is known as a corespun thread. The core is made of polyester which is wrapped with cotton fibre. The thickness of the thread is expressed in metric numbering (NM). You can find out more about thread numbering in Madame Sajou's Diary. This is is the 28/2, so a thickness of 28 twisted in two strands, or ply. The diametre is 0.38mm and each cone contains about 3500 metres of thread. ATTENTION: these threads are available only on order.Delivery times can vary according colours and quantities.