(1 seat ) refers to 1 piece of normal cover which is avaliable for the length between 90 and 140cm; (2 seats ) refers to 1 piece of normal cover which is avaliable for the length between 145 and 185cm; (3 seats ) refers to 1 piece of normal cover which is avaliable for the length between 190 and 230cm; (4 seats) refers to 1 piece of normal cover which is avaliable for the length between 235 and 300cm;