Head harness
From wipipedia.org
A head harness is a bondage device made up of a a number of straps that encloses the head. The head harness may be used to hold a gag or blindfold in place, the harness may also hace D-rings to allow the head to be secured as part of a more complex bondage proceedure.
The head harnes can also perform a similar function to a hood in that it depersonalises the wearer which can enhance the power dynamic in a scene.