I got 2 of these washers, they are split, you just pull the spring back a bit and roll the washer on the end.Is that the washer that is sold on eBay?
If so, one photo makes it look like it could be mounted between spring and end of guide rod but I don't know how that would be possible. Another photo shows the washer in the slide by itself. So do you install the washer by putting it into the slide first and then insert the recoil spring and guide assembly?
I would assume that if the washer is first inserted into the slide first then the spring will be compress a very small amount but should not increase the tension on the spring significantly so should not negatively affect the cycling of the slide.