Make sure that you new seats are not a fire hazard. What kind of material are they made of? This is important to consider. The material should be fire retardant. What type of swivel function do they have? Maybe they swivel all the way around. Perhaps it is only half way around. You may not want any type of swivel. A swivel may present a hazard to small children. Shop at a quality supplier. They will weld the swivel function for you. This will keep the seats stationary.
Styles - Find a seating supplier that gives you a large selection to choose from. This will give you the best options. Make sure that you get the right size, too. How long is the counter? You will need one seat for every two feet of counter length. How high is the counter? Take the measurement and subtract one foot. This is how high the seat should reach. It should be one foot from the counter. Maybe your seat is not a standard height. You can order custom made seats if you need to.
Which type - What kind of seating are using for your new project? Is it a conventional look. The old fashion kind with no back, are still popular today. They will turn 360 degrees. You might wish to use seats with backs. Maybe you want the type that resembles a regular chair. All of these are possibilities.
Is this on a deck or patio? That will not be a problem. You can find seats that are made for outdoor use. They will be available with backs or not. Maybe you would like a logo on the seat, also? Some may have that option available.
Material - You may wish to use wood. Metal may be a good choice also. This will depend on the look that you wish to achieve. These seats may take a lot of abuse and use. Buy ones that are durable and come with a good warranty.
Final thoughts - You may be creating a new project. Maybe you just need new bar stools. Find a good quality supplier. Check out all of their options. Purchase long lasting seats. Pick ones with a good warranty.