Thru-hiker.com has added the ykk #3 coil water resistant zippers sold by the foot. The reg #3 coil is about 10gms/yd and the water ressistant is about 12gm/yd and the #5 WR is about 20gm/yd. I've been using the #3 WR on bags and bivys for a while. The WR design eliminates the need for a draft flap on most bags/ items and the added stiffness works fairly well as an anti snag strip. Regular #3 zips pulls and double sided zip pulls both work on the WR. Note that single sided pulls are WR specific and face backwards and so I recommend using the double sided pulls for convienience. Putting on the pulls is very easy since the edges are stiffer than the reg #3. The #3 is a bit more fragile but I have not have any return or complaints yet. AS will any SUlL item VS a heavy weight item, a bit more care is required. Lube the zip from time to time.