This is my 6th time buying this product because for the price it's the best tape a tiler could ask for. I regularly cover this tape with mortar and water. It will not rust, although the numbers will wear out over time. Therefore, as a professional, I give it 4 stars for solid design, low price, no rust for about 4-6 months. How long do you think the tapes will last? I've tried at least 10 other brands in my career and can say I don't mind buying 3 of them a year. π