This SAE Standard was developed primarily for passenger car and truck application, but may be used in marine, industrial, and similar applications. The purpose of this document is to provide dimensions for the different pressure ratings of bayonet type radiator pressure caps and filler necks. Use of these dimensions will preclude the use of a high pressure rated cap on low pressure systems for the small and medium size applications. This document will allow use of low-pressure rated cap on a nominal high-pressure system.