4 31/32 in, Inside Dia. 13/32 in, Includes O-Ring, Thread Size Not Applicable. Air Filter Element by Baldwin Filters®. Clean air is vital to maximizing the performance and longevity of your engine. Keep your engine dirt and contaminant free with the Baldwin PT8971-MPG. Baldwin, an industry leader since 1936, carries a full line of Heavy-Duty Air Filters and Elements to meet your air intake needs. This first-rate American-made product is the winning choice for performance-minded racers. Made with craftsmanship and high-tech machinery by highly skilled engineers, it leapfrogs the competition....