It’s a personal opinion, but I love this type of gag in a scene. A big ball gag is visually impressive but tough to handle for long. The classic cleave gag isn’t all that effective. This type – known as the Whitehead Dental Gag – is easy to wear but opens you up to all sorts of intrusive penetrations. Mixing it with watersports can be particularly hot.
I believe this is Hong Kong based pro-domme Mistress Elis Euryale. You can find her professional site here and her twitter feed here.