u can use normal orange ust 6 mm soft silikon katheter! it dont hurts never i hade pain also eaven when i am really junge boy with 12 i do it with all kind of toys i found!! but 6 mm is normal thin sice! 4 mm are to hard and hole in front u can ripping littele ur slime kin in ur peehole if u wanking in it ur peehole with ust 4 mm harder katheter! hey are mutch to hard those 4 mm katheter material isnoit good for fucking in ur urethra! orage soft is better and never u destroy ur inside slime skin with orange katheters! the soft orange silikon -rubber katheter ist best for it! BUT ALL U USING DESINFEKTION IT IS VERY IMPORTAND ALSO UR HANDS!!! and do with nedael less do slime gelee in ur urethra first! better moreus less! i do it with that doctorsare uaing at blut taking but no neadel using!! ok
Maybe don’t cath with an erection? The sphincter at the base of your bladder is clamped tight to prevent retrograde ejaculation. Catching while erect (or even semi-erect) will damage it meaning you’d likely start getting semen in your urine and possibly dribble when you bladder starts to get full.