I think they're talking about a strong glue that Hair Club uses to 'fuse' the hair system to the scalp. This 'hard bond' lasts for 4-6 weeks or until your next appointment with Hair Club per your maintenance contract. It gets you from one appointment to the next without you having to do anything. I don't believe this is sanitary to bond for this long a period without removing the hair system and cleaning your scalp. Some people might comment that the scalp would get itchy going that long without taking the unit off and properly cleaning the scalp. Hair Club has a solution for that. They are glad to sell you a bottle of a product called 'Alive.' It's an scalp cleanser that you squirt through the base of your unit and it dissolves (or eats) the crude that has accumulated on your scalp. I just think that there is no substitute for removing the unit, cleaning the scalp, and then doing a fresh re-attachment. It's more sanitary than the 'hard bond.'