I have a strong cob!!! Although I can ride him bitless I feel I need something more for roadwork, considering he galloped off down the main road with me once. (eeek!). He was in a mullen mouth because I like to use the mildest bit possible, however safety has to come first. I bought one of the Australian Pee Wee bits for him and feel that if he tries it again I have control over the situation. I just use the Pee Wee on the snaffle rings, but there is an option to use it on the lower rings and this is recommended for eventing (although it is highly unlikely he will be doing that, being a big hairy cob!) If you `google` in Pee Wee bit you can get onto the website which tells you all about them. I bought mine from a supplier in this country, but you can order direct from Australia. The sizing is a bit strange, being only two sizes. I would say if your horse takes anything over a 5" size bit, or even 5" then go for the larger size. Hope this helps.