Personally i am not a fan of the whole chastity play thing. Yet i noticed there are different sizes available. Go for one that suits you best.
When you apply it, make sure you are in a state of non-arousal. Plus: an ice water shower will do wonders!
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Regards.