It's use full because it protects the clocks in manufacturing dusty areas and protects the key pad from certain types of light damage. I fill it should be an automatic add on from Swipeclock on every clock purchase. It's a great value to all customers. if you sell 1,000 per month then it's 20,00 in revenue per month and 240,000 per year. Thank you layne 541-499-4455
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