Part No. 52-208.KS (oro2u.com)
TOP END GASKET KIT FOR HONDA TRX-400EX (99-09)
Top end direct OEM replacement gasket kit from K&S Technologies includes all gaskets, washer and o-rings for a top end rebuild.

Cylinder Head Gasket
Cylinder Base Gasket
Cylinder Head Cover Gasket
Tensioner Lifter Gasket
4 x Valve Stem Seal

2 x Exhaust Pipe Gasket
4 x Valve Guide O-Ring (10 x 1.6)
Cylinder O-Ring (88 x 2)
4 x Tappet Cap O-Ring (35.5 x 3)