The primary factors that affect hose performance under vacuum are hose size and construction, temperature and bend radius. Hose construction determines the ‘hoop’ strength or the relative ability of the hose to resist collapse. Generally, smaller ID’s, thicker walls, external reinforcement such as wire wrap or covers and bonding together the hose layers serve to increase hoop strength. As the temperature of a hose increases, the hoop strength typically decreases due to material softening. As a hose approaches its static bend radius limit, hoop strength can be adversely affected because the hose profile will go from round to oval. If combinations of these factors exist (i.e., large ID, thin wall, high temperature, extreme bending) hoop strength is reduced even further.