Thank you for contacting Product Support. No it is only made to hold one 12X13 insert at one time. You should order two inserts so that when you are using one the other can be getting cold in your freezer and will be ready when the one in your wrap gets warm.
1 Being overweight: Excess body mass can decrease blood circulation, causing fluid to build up in the feet, legs, and ankles.  Standing or sitting for long periods: When the muscles are inactive, they canât pump body fluids back up toward the heart. The retention of water and blood can cause swelling in the legs.
Sometimes swelling can indicate a problem such as heart, liver, or kidney disease. Ankles that swell in the evening could be a sign of retaining salt and water because of right-sided heart failure. Kidney disease can also cause foot and ankle swelling.