The trapezoidal shape is said to eliminate the possibility of the O-ring popping out, unlike standard round-shape O-rings that rely on being pinched by the groove retaining ring for seal retention.

O-ring sealing systems are ubiquitous in oil/gas field applications and have been extensively tested. The general relationships between O-ring designs and their performances are well known; however, O ...

For more than 60 years, engineers specifying seals and customers using them have accepted the arbitrary rule that the maximum amount O-rings will swell in most applications is a 25% change in volume.