The ATV tires within this category are all available in the selected size; 21x8-9. The numbers 21-8-9 represent the dimensions of the tire. The first number is the height, the second number is the width & the third number is the diameter of rim that it will fit on. The width of the rim is not as important to know. As long as the width of the tire is greater than the width of the rim they should mount together just fine. You can usually go up at least 1 size from your stock tire sizes without having any problems, both in height and width. Contact us if you need some help.