Johnson flaps are two piece construction: a center flap with U-shaped 'gasket' piece both constructed of clear, tinted, flexible vinyl. Tinting has varied in density over the years. This design, which was apparently intended to seal well, has led to some confusion on the part of customers attempting to replace their flaps. Some measure inside (the opening available to the pet) and others measure the full outside dimension.

What is presented below is "Inside" the U-shaped piece. Focus on the width as that is the easiest to measure accurately.

Magnets are embedded in the flap corresponding to iron 'keepers' glued to the aluminum or plastic frame. Neither the magnets or the keepers are available separately.

Johnson sizes have size notations, S-2, M-2, L-2 or XL-4, embossed on the flap. We have seen some exceptions to this, however. A very few flaps have nothing on them.

Since PetSafe bought the Johnson Pet Door company, they now package these flaps labeled "PetSafe".  Don't be confused; it's the same flap.