It's the bumper cover. 2001 looks just like the one on your car now, but instead of saying Mustang it says Cobra. Now the one in your example, is an 03-04 Cobra rear cover. That's what I put on my 99 Cobra. It looks so much better than the 01.
__________________ C&L 80mm mass air and True Flow pipe, Mac CAI, BBK 65mm tb, Steeda non-piggy back ud pulleys, MGW shifter, RAM HD clutch and aluminum flywheel, 3:73 gears, 2.5" Dynomax o/r x pipe, 3" MAC cat back system w/ 3 1/2" tips, Kenny Brown(front and rear strut tower brace, caster plates, subframe connectors,extreme matrix brace,jacking rails, torque brace, lowering springs), Bilstein shocks, 03-04 Cobra(side scoops, rear bumper cover, top), 6pt roll cage, white FR500's, FMS 2000 Cobra R air dam. | 
1999 Mustang Cobra rear bumper help 
