▁ring ▁may ▁be ▁made ▁of ▁hard ▁or ▁soft ▁material . ▁These ▁two ▁rings ▁are ▁mach ined ▁using ▁a ▁process ▁called ▁la pping ▁in ▁order ▁to ▁obtain ▁the ▁necessary ▁degree ▁of ▁surface ▁finish ▁and ▁flat ness . ▁ ▁The ▁se al ▁ring ▁is ▁flexible ▁in ▁the ▁ax ial ▁direction ; ▁the ▁m ating ▁ring ▁is ▁not ▁flexible . ▁ ▁Se al ▁ring ▁ ▁By ▁definition , ▁the ▁se al ▁ring ▁is ▁the ▁ax ial ly ▁flexible ▁member ▁of ▁the ▁end - face ▁mechanical ▁se al . ▁ ▁The ▁design ▁of ▁the ▁se al ▁ring ▁must ▁allow ▁for ▁minim izing ▁dist ort ion ▁and ▁maxim izing ▁heat ▁transfer ▁while ▁considering ▁the ▁secondary ▁se aling ▁element , ▁drive ▁mechanism , ▁spring ▁and ▁ease ▁of ▁assembly . ▁ ▁Many ▁se al ▁rings ▁contain ▁the ▁se al ▁face ▁diam eters , ▁although ▁this ▁is ▁not ▁a ▁requirement ▁of ▁the ▁primary ▁ring . ▁ ▁The ▁se al ▁ring ▁always ▁contains ▁the ▁balance ▁diameter . ▁The ▁shape ▁of ▁the ▁se al ▁ring ▁may ▁vary ▁consider ably ▁according ▁to ▁the ▁incorpor ation ▁of ▁various ▁design ▁features . ▁ ▁In ▁fact , ▁the ▁shape ▁of ▁the ▁se al ▁ring ▁is ▁often ▁the ▁most ▁distinct ▁ident ifying ▁characteristic ▁of ▁a ▁se al . ▁ ▁M ating ▁ring ▁ ▁By ▁definition , ▁the ▁m ating ▁ring ▁is ▁the ▁non - flex ible ▁member ▁of ▁the ▁mechanical ▁se al . ▁ ▁The ▁design ▁of ▁the ▁m ating ▁ring ▁must ▁allow ▁for ▁minim izing ▁dist ort ion ▁and ▁maxim izing ▁heat ▁transfer ▁while ▁considering ▁ease ▁of