Snoozer Luxury Lookout Pet Car Seat, Small Luxury I, Anthracite/Black

Q: What are the inner dimensions? It doesn't look deep.

The pet car seat works perfect for my dog 18lb Havanese who has short legs. The seat does not look deep but does the job well. He had been car sick before and seat solved problem. Now he can see out easily and is secured well. Makes his ride better and mine safer. Back 8" high, 7" on sides to front, and the front is 4 1/2".

Q: Does the medium size include two containment straps, or is that only the large? i need to put a chihuahua and yorkie together.

It only has one but you can order another as your pup family members are small. I have a 12 lb and a 16 lb pupfamily they both fit but it is tight that is why I purchased 2. My 16 lb girl likes to chew her straps so I am always replacing them. You will really like the seat and they will be safe and you will have piece of mind. My girls love them

Q: Will my 30 Pound dog fit into the medium?

John my dog is 25 pounds and she fit into the small. She's a staff/pit bull runt. her mom is 31 pounds and she also fit into the small lifejacket

Q: Do you need to buy a special harness or can I use any harness?

It doesn't need a special one, just one that has the loop on the back of the harness (not high on the neck area). I have two of these for two different dogs obviously, and they both use different harnesses (one is a puppia, and one is a Gooby). These are the best car seats. I just replaced one that was 12 years old!!