Also known as Swiss balls, exercise balls, balance balls or fitness balls, stability balls have the versatility to be used for a range of exercises. But, stability balls come in a variety of sizes, with different features and made of different materials. Comparing stability balls helps you choose the right one, based on your size and fitness goals.

Size

The most basic feature of stability balls is the size -- typically given as the diameter in centimeters. Common sizes for stability balls include 55cm, 65cm and 75cm, but you can also find them with a diameter of 35cm or 85cm. The size you need is based on how tall you are. To test for fit, sit on the stability ball; if it's the right size, your knees should be bent at 90 degrees.

Features

An elastic, soft plastic vinyl or PVC is the most common material for stability balls. The main difference in the material is the overall thickness of the PVC. Lightweight or inexpensive stability balls will have a thin layer of PVC that may allow air to leak from the ball. This ultimately results in an unsafe stability ball that could potentially pop under excessive stress. Stability balls with a thick layer of PVC can withstand heavy users or more robust exercises.

Types

While the most common type of stability ball is the traditional round ball used for abdominal and core training. You can also buy reinforced, extra-strength stability balls, which are designed for heavy-duty use to withstand exercises such as the bench press with a weight. You can also find weighted stability balls, which keep the stability ball positioned in one place.

Benefits

Regardless of the size, material or type, all stability balls have the potential to provide numerous health benefits. According to Cindy Brotherston, certified personal trainer, stability balls can help improve muscle strength and endurance to alleviate or prevent back pain. Stability balls can also improve core stability to help support movements, or improve flexibility through stretching exercises.

Considerations

Most stability balls will cost from $10 to $50, as of 2010. Some companies include accessories, such as an exercise video or exercise mat. As a general rule, inexpensive stability balls feature a thin layer of PVC and may not resist punctures. Another consideration for stability balls is the color, with common colors including red, blue or purple.