Type H: O-ring groove
<img src="https://eng-calculations.com/SVG/EN/EN_1092-1/Type H(and58) O-ring groove.svg" alt="Type_H(and58)_O-ring_groove" title="Type_H(and58)_O-ring_groove">
https://eng-calculations.com/SVG/EN/EN_1092-1/Type H(and58) O-ring groove.svg