The type of carrier you choose depends on your needs...and the size of your pet. Obviously, dogs weighing more than 25 lbs. can be difficult to haul around in a carrier. Of course you can always get a wagon to pull your 150-200 lbs. Mastiff.
Actually there are airline carriers made for large dogs who can't accompany their humans in the passenger area of the plane. These carriers should be escape-proof, large enough for your dog to stand up, turn around and lie down in. They should be well-ventilated without your dog being able to stick any part of his/her body out and they should be leak-proof. Your information - name, address, destination and address, phone numbers, any special instructions, Live Animal labels and This End Up labels should be attached to the top and sides of the carrier.
Avoid wire carriers as they can cause injuries. Contact the airline beforehand to make sure about their procedures. Check with your veterinarian to see if it's advisable to feed your pet before traveling or if any medications are necessary.
As an alternative to having your dog travel in the cargo area, there are now pet airlines that will transport your dog in more comfortable, safer circumstances.
If your cat or dog weighs 20 lbs. or less they may be allowed to travel with you in the passenger cabin. There are soft-sided carriers that can be used. Have food and water dishes available and waste disposal materials.
At home there are many different styles of carriers for your cat or dog weighing 25 lbs. or less that allow you to take your pet with you almost anywhere you go - shopping, visiting, hiking, etc.
If your pet enjoys bicycling with you, there are baskets and seats, some with covers, all with restraints to keep your pet safe. Some fit on the back of your bicycle, others in front, your choice.
Some designer carriers look like large shoulder bags or bags with handles. They are available in many colors and patterns to suit your taste.
Available too are backpack or front loading carriers that look almost like baby carriers. Some have openings where your pet can sit forward with room for paws.
There are sheered carriers and strollers with or without detachable carriers. Some are enclosed with vents for air and are clear plastic so your pet can enjoy the sights.
With the many types of carriers in favorite colors and patterns, you can have your pet stylishly join you in all your activities.