Top Mount Filler Breathers are designed to be used as a filler port for tanks, hydraulic power units or other fluid containers. These units also let the tank breathe while keeping out airborne particles. Standard Features: Bayonet zinc plated steel cap -- large capacity Twist to lock removable cap breathes and filters air Concealed air vents allowing for outdoor applications Flute finger inserts for easy gripping (vented style only) 10 or 40 micron filtration available (vented style only) Safety chain -- prevents loss of cap Heavy duty Cork-Neoprene gasket provides a positive seal between flanges Zinc plated flange -- bayonet flange (SAE J829) Strainer basket 4 inch long nylon with solid dome bottom to prevent punchout 3 inch long stainless steel, 30 mesh Thread forming screws -- prevents particles from entering reservoir during installation by forming threads rather than cutting them