Yes definitely, all covers are interchangeable with the same sized inners. 

Extra covers can be ordered by contacting us or directly on our website.

In the case of the large and XL sizes, the Comfyzak has the unique feature of being able to repurpose its inner sacks (sacks with the foam stuffing inside) to make 2 smaller Comfyzaks, all that being required are 2 smaller covers and visa versa.

Large = can be repurposed to create 2 smalls (2 small covers needed)

XL – can be repurposed to create 2 medium (2 medium covers needed) 

visa versa.