Mechanical Retrievable set Packer,When running string tools as required height, steel ball moves from end side of short slot to end side of long slot. Slip open to touch casing surface. String weight compress rubber element to enlarge diameter, which could seal and block oil and get annulus. Pull up string tools, steel ball move to end side, cone-shaped seat leaves slip and slip return back, rubber element return back and unset Packer meanwhile.