What is up with walkers always having tennis balls on the back posts to help them slide along?Do they come like this? or are all these geriatrics customizing their "whips" with some fresh dunlops or some sick ass penns. Just a thought, but maybe these walker manufacturers should work out a deal with Wilson, like buy a walker get a can of tennis balls for free. That's three tennis balls: 2 for the walker and one spare. Or they could just make them so they slide better.