I have a bull mastiff and lab (we think, not too sure of his sire) mix breed who is 5 years old. He is a wonderful dog and I would recommend this mix to anyone. He is calm while in the house, well mannered, easy to train, gets along great with other critters (we have a Chihuahua, parakeets, a large iguana, and a Chinchilla, plus he has been around cats and many other critters), but is protective when we are not home and is a great outdoor dog. At the lake he will spend hours playing in the water, hiking, or playing with us. If a squirrel or groundhog runs from him, he will chase it, but on the rare occassions that he has actually caught something, he didn't kill it, just sat there staring at it until it got up to run again. If it didn't run, he didn't mess with it other than to smell it. He is also wonderful with children. Little ones can wallow all over him and all he does is look at me with a "help me" look. He doesn't require a lot of attention, but is ready to play when you are. He is about 85 lbs. though, and that may be a little larger than you are looking for.