I got the zipyard to add one half of a zip to some kevlar motorcycle jeans to attach to a motorcycle jacket. I called before taking the jeans to them to specify kevlar thread since it's a safety alteration to ensure strength in the case of an accident and sliding along tarmac. I was told I didn't need to supply the kevlar thread as they had some and would use it. To attach a zip cost over £50, and they used a single line of thin cotton/polyester thread, and I then had to get them to strengthen it with more standard cotton/poly thread. All in all it was expensive and indequate. I wouldn't recommend them for motorcycle clothing.