The plastic liner/base is effectively useless. It's as thin as a piece of paper and shreds apart within a matter of days. I'm not sure where the 'indicator system' on these mats is located, but I was replacing them constantly due to the liner issue and the lack of odor absorbency. Also, the 1 1/2" adhesive Velcro strip that comes on the mats to hold them in place is just as useless. I had to attach some 3M VHB tape to other points along the perimeter of the mat to even get it to stay put. If you have a high traffic area and you want your restroom/locker room to look and smell nice, look elsewhere.