O.S. Engines 45925100 Muffler for F4020 FS70-91II FEATURES: Fit pumped and non-pumped versions. Constructed of aluminum with pre-drilled pressure tap hole INCLUDES: One Silencer Body for the F-4020 Exhaust System used on the O.S. Max FS-91 Surpass II engines with, pressure tap and 3.4mm x 4mm screw to se