I am looking to replace the coping and liner on my old Fox Pool. The coping "slides" onto the straight metal wall. It is a flat back kidney design 36' x 18'
That is a proprietary coping that you will have to buy from Fox directly or someone that sells/installs Fox pools. I would start by reaching out to them and they may end up providing you with a list of Fox pool dealers/installers in your area. You should be able to get what you currently have or the cantilever variety that allows you to use stone or a poured concrete edge with foam forms.
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