Tips on Skirt Size The cover has a flap (typically 2-4 inches) around the edges of the spa called a skirt. The skirt must easily sit over the edges of the spa, with a little room to spare. You can either measure your existing skirt length or use the default measurement for your particular spa. The longest the skirt can be is 6 inches. You will want this to hang straight down. So, if the lip of the spa is at an angle, make sure you measure the cover long enough to achieve this. Also, measure the skirt long enough to cover the spa lip, or the spa cabinet rim. If you have any questions about this, please contact us at 1-877-551-5520.