For protection, the case is equipped with soft rubber lining, which also ensures that metal doesn't touch your watch. (indabaa.com)
Thus the setback wheels are rubber lined so that they do not damage the floor in any way. (babywalkerpro.com)
The included non-slip rubber lining on the base means that it's stable, won't slide, nurtures perfect form and is safe to use (prevents strain and injuries during use). (epitomiefitness.com)