I bought one for use with my partner. She loved the flanger but wasn’t thick enough for her to hold in place without me applying a little pressure to hold the base in contact with her.
Positives.:
She loved the shape and thickness of the large deviant. and had 3 orgasms without even turning the electricity on.
Negatives:
The large deviant was just a little too long for her and we never managed to get the device far enough into her to allow the base to make contact with her - so we were never able to use it for its intended purpose. The device is no longer than she is used to accommodating but the girth seems to prevent her taking the full length
Overall I would say the deviants are excellent devices but consider if you or your partner can take or the large deviant or if a medium would be a better option