The fund offers multiple share classes, which are subject to different fees and expenses that will affect their performance. (franklintempleton.com)
Some other indices include multiple share classes of the same company meaning that an investor's economic exposure to the company can be larger than it appears. (indexologyblog.com)
There is, however, a requirement to use the lowest cost share class if multiple share classes of the same fund are available. (kitces.com)