Phelps Style 9004 is a Spiral Wound Gasket for STG (Small Tongue Groove) flanges, and is only available for ASME 16.50 flanges. Compression of the sealing element is controlled by the use of the correct flange face configuration - therefore, spiral wound gaskets are recommended for tongue and groove, male and female and flat to groove flanges only. Groove depth is equal to or less than tongue height.