And volleyball players have to stay on their own side.
But basketball players can run up and down the entire court freely.
You should leave out all personal material and also any irrelevent details about the items themselves--details that have nothing to do with the division of items into classes.
The second difference is the size of the ball and how hard it is.
It would be nice to start off with an Introduction--a short paragraph that will introduce the topic and inform the readers how many classes we are going to divide the items into.