[Tom Goldman]

Ken ,it's the inside seat width , best way to determine what you want is while sitting, measure across your hips .
I doubt you would need bigger than a 17" style .
I few of my customers have had custom covers made ,some have used the covers Kirkey offers as patterns .
Kirkey's seat covers are actually fairly nice and pretty rugged . ...I usually add a some foam in the lower lumbar area for more support to the lower back