I remember a customer who wanted to have gut on the very nice month duration Dachluhren he bought from me. While I tried to talk him out of it, he was pretty adamant about how original he wanted the clock to be. I bought the best fine diameter gut that was available. 6 months later the gut separated, dropping the weight and punching the base off of the case.
If a customer is adamant, I will use gut - with the provision that I am not responsible if the weight falls. And yes, I love the look of gut, but I honestly prefer not having perfect round circles punched into the inside base of the case. So, I use a modern, braided fishing line that is ridiculously strong and of a small enough diameter that it does not over-fill even long duration winding drums.
And yes, I have had many discussions with customers and other dealers, my bottom line is that the weight lines are a disposable component of the clock – much like the oils I use to lubricate the pivots. Or even the wax I use to protect the finish. My goal is to provide each customer with a clock that will not have problems with broken weight lines. Ever.
The product I am currently using – by Power Pro – is a dark grey in color. I have not managed to find a comparable product in the brown/tan of gut. But, fortunately, my customers have all liked the look of the line.
Needless to say, this recommendation is based on my best practices. It is not a warranty for this or any product recommended on this site.