Best used on the original Aquatera Chinook (with a small round hatch on the bow). Fits the stern of some Aquaterra brand kayaks circa late 1980s through mid 1990s. Original Aquaterra Perception hatch covers are sometimes marked as Large L on older kayaks or Medium M on more recent kayaks. Some of these Large and Medium covers are actually the same size, others are not. If your Chinook kayak is much older, circa late 1980s to early 1990s, or your old hatch cover is marked L this is your best bet. If your kayak is not a Chinook, or made in the mid-to-late 1990s use the Perception Medium Neoprene Hatch Cover.
This cover fits the raised lip of the stern hatch opening, approximately 21 x 16 inches out side dimensions.
This is the inner stretchy fabric cover that goes under the hard plastic strap-down cover. (Both covers must be use together for a watertight seal, outer cover not included.) Cover measures approximately 19 x 14 relaxed. Neoprene hatch covers stretch about 2 inches larger than relaxed dimensions listed here. Cover may bear the one of the following names: Chinook, Aquaterra, or Large. PERNEO
Info Link: Kayak Hatch Replacement Options Part III - Double Covers: Neoprene Inner Cover - Outer Hard Covers