If it helps when I was with my exgf she was into rough sex. She enjoyed being with guys much larger than me, in every way, and loved the roughness of being mauled in a group session. It was not my cup of tea, I told her this often but when went to swing clubs she would look for the roughest and toughest guys there and sure enough she got what she wanted. One morning after one of these sessions I asked her why she enjoyed it so much and her reply was don't knock it until you have tried it so I agreed to try it upto the point of me saying enough.
She came to my house with a bag and when I asked what was in it she said wait and see. We started to get amorous and we were soon naked me playing with her and her playing with me. Out came her bag of tricks and firstly it was a silicone tube that fit tight but snug around my scrotum to sort of exaggerated the size of my balls. She started to walk my cock and suck hard on each ball in turn, the feeling was tremendous, but as I was about to cum she reached in the bag and brought out a long bar made up of tiny ball bearings and pushed it into my little eye. At first I was shocked but it soon felt great as she worked it in to its full length (around 18"). As I cum it started pushing past the little balls. After that first initiation into CBT she would bring more rigorous things until I said no to what looked like a traffic cone and I said no fucking way, so she used it on herself. It looked painful, but she was loving it she explained later it was what she used on herself when she got horny at home.
All in all I found some nice, some not so nice and some I would not even dare to try so go easy at first, if you go ahead with it, and when you find your limit just say no
