Mirro 3440 Gasket Mirro, Mirro-Matic Canner Gasket 3440 Mirro Pressure Cooker Seal/Gasket Part Number S 3440 and 3440 S (opn) USA MADE!! S3440$21.99 Order before 2:00 PM ET this item will ship same day. Orders placed after 2:00 PM will ship next business day! Soak gasket in hot water 10-15 minutes before using. Rinse and dry thoroughly. Any residue released from rubber is harmless. Lubricate gasket lightly with cooking oil or shortening the first 1 or 2 times only. Place pressure cooker gasket in lid of pressure cooker. (If gasket is a little big this is typical of the Mirro pressure cooker gaskets.) Lay the gasket out as flat as you can get it to lay, not looped in one place but wavy all the way around. Put lid on pressure cooker. go ahead and use pressure cooker or boil water in pressure cooker and let cool. The new gasket will seat in to lid. See Pressure Cooker book for more detailed information..