常用的R型垫片按截面分为椭圆型或八角型，标准的R型环形垫片按API 6A以及ASME B16.20标准尺寸制造，使用压力是10000PSI。
　　在梯形槽法兰中八角垫与椭圆垫可以互换。RX型八角垫适用于压力增强的标准R型环状垫片，适合于R型一样的法兰槽密封面。BX型八角垫适用于压力增强并且设计应用高达15000PSI压力系统。有多种材质及形式适用于不同的设计与操作要求，参考材质特性表。
　　注意：选用八角垫材质硬度应低于法兰面15~20HB,而且建议不要重复使用。
　　金属环垫按截面分包括椭圆垫，八角垫,特殊形式的八角垫RX型和BX型透镜垫几种形式。
　　ANSI B16.5-1973、JPI-75-15-70、GB 699、GB1220、JB755、HG20633-97
　　金属八角垫片的几种主要形式：
　　R型 椭圆垫 R型 八角垫
　　RX型 八角垫　耐压可达700bar
　　BX型 八角垫　耐高压(可达1500bar)
Metal ring gasket is made of metal materials into the section shape is octagonal or elliptical solid metal gasket, having a radial self tight seal effect. The metal ring gasket cushion plate and flange of trapezoidal grooves of the inner and outer side surfaces ( mainly outside of the outer side) contact, and through pressing and forming a seal. Metal ring padMetal ring gaskets originated from the United States, in the nineteen twenties was first used in boiler field, used for the manhole cover, autoclave and other container sealing, later in the oil production and oil refining industry attracts more and more attention, with the steam temperature and pressure increase, metallic ring gaskets have been used more and more widely. Metal ring pad used for nominal pressure is 2 ~ 42.0MPa.2, classificationMetal ring pad is divided into octagonal ring gasket and elliptical pad two. Metal ring gasket according to the cross section shape is octagonal and oval two structure.Octagonal ring gasket and the flange groove matches, mainly for surface contact. The oval ring gasket is compared, although not easy with the groove in the flange to close together, but can use again, and because the section is composed of straight lines, easy processing. Oval ring gasket on the flange groove is line contact, better sealing performance, but requires high processing precision, thus increasing the manufacturing cost, at the same time oval ring gasket can not be used repeatedly.In 3, the gasket standardsGB / T9130-2007; JB / T89-1994; SH3403-1996; HG20633-2009( American system ); HG20612-2009( European system );In 4, the gasket characteristicsIn 1, high temperature resistance, high pressure resistance, suitable for high pressure flange seal;2, durable and reliable;3, adapted to the load frequency variable working condition;5, corrosion resistance and low hardness of metal ring padCorrosion resistance of low hardness metal ring pad : the custom of low carbon content of trace elements in metal materials, adjust, change the ordinary heat treatment methods to ensure the implementation of low hardness metal ring pad. Products are widely used in petrochemical, chemical, metallurgy, refining, gas, nuclear power, thermal power and other industries of high temperature, high pressure equipment, process piping static sealing parts.