Every Essential mattress is 13cm (5.1 inch) high. We offer the sizes below to cater for most families in Hong Kong: Small Single - 76cm x 183cm Single - 91cm x 183cm Long Single - 91cm x 189cm Twin - 120cm x 183cm Long Double - 135cm x 189cm The mattress may have an up to 2 cm difference in their measurements/ dimensions. It will not affect the function of the mattress.