These Fetch Balls are made from 5/16th inch heavy duty firm halter cord.
They come in three sizes:
1.  Large - Slightly bigger than a tennis ball
2. Medium - Slightly larger than a racket ball
3.  Small - Slightly lager than a super ball
These come with a velcro strap that allows you to attach it directly to the leash so you don't have to carry a dirty, wet, muddy ball after a long day of throwing it for yor dog
They come in a variety of vibrant and dark colors