The Cometic C9689 is a pair of multi-layer steel (MLS) cylinder head gaskets designed for select Harley-Davidson Evolution Big Twin and Sportster motorcycles.

It features a 3.500-inch stock bore size and a 0.040-inch thickness.

Vehicle Fitment
Harley-Davidson Evolution Big Twin: 1984–1999 (Excluding Twin Cam)
Harley-Davidson Sportster 1200 (XL1200): 1988–2022 (Excluding XR1200)

Technical Specs
Bore Size: 3.500 in (Stock Bore)
Thickness: 0.040 in
Material: Multi-Layer Steel (MLS) with Viton outer coating
Quantity: Sold as a pair (2-pack)

Key Features
Outer layers use embossed spring steel coated on both sides with Viton rubber to seal rough surface finishes.
Center shim layer is uncoated stainless steel.
Even clamp load distribution reduces bore distortion and improves ring seal.
Does not require extra sealants or re-torquing after initial installation.