Air Force garden rock heavy duty abs plastic mold.. Great for casting plaster, concrete, resin, wax and more. This mold will cast many, many times with proper use.
When cast the finished rocks will measure 7" x 5" x 2" thick.
Rapid set cement all from Home Depot works great with this mold too which is fast setting and allows you to produce many of these stones in a day. See Army, Navy and other services too!