It is difficult to make a recommendation for a product without knowing what the application is.
Tough Skin 20 by OX is a synthetic underlayment. There is currently not an ASTM Standard for synthetic roof underlayment.
We are inclined to use and recommend only products that are ASTM and UL Tested and Approved.
Was your question regarding tile roof application?
To find a very good asphalt felt for tile underlay, stay with ASTM D2626. That designation is for Modified Asphalt in a Type 40 Felt. It is a very good product.
Up a notch is an SBS Modified Felt with ASTM D4601.
These products are well designed and tested. The roofing underlayment on the market today will have the UL Approval and the ASTM number on the wrapper.
Thank You for your question.
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