This mould is made from thick semi-rigid ABS plastic.
Each Garden Stone you make will measure approx. 7½" x 6½" (19cm x 17cm) and they will be just under 1" (22mm) deep.
Just in case you'd like to make garden stones for houses with more than one cat, you'll find a larger version of this mold here:
SPOILT ROTTEN CATS LIVE HERE GARDEN CONCRETE MOLD