Adaptor Plates are an easly way to mount an aftermarket seat to an existing bolt pattern in a truck. It is wise to measure before ordering any seat and double check if an adaptor plate is needed. He have included these same plates as options when you purchase a seat. Typically Volvo and International trucks have a wide mount seat that does not follow the standard aftermaket bolt pattern.
It only takes a few minutes to measure your current bolt pattern. Make sure to check it before you buy!