Is a 3 inch diameter object to large for the anus?

Not really. however when inserting anything into your anus, you must be careful that you do not injure yourself. Always use a lot of lube and warm your self up beforehand.

II know from personal experience it is possible to take an dildo of 3.5 inches in diameter with training. It is an addicting experience. I am working to take myself up to 4 inches.

Just take it easy. Finding a pertner to help is great. Mine are also men.