The standard seal is constructed of durable black Buna N Compound, providing long-lasting protection for air lines. The "Guardian" seal includes a rubber flap and metal seal screen, effectively safeguarding against debris. Sold individually, this versatile seal fits most makes and models, making it a practical and reliable choice for air line maintenance. With its durable construction and protective features, this seal is an essential component for ensuring the smooth and efficient operation of air lines, making it a valuable investment for any application.