The full cut out version with no inserts is recommended for asphalt. I have another version coming that is cut out but has the inserts installed in it so you can keep them there and run it on carpet.
After getting fed up with constantly having to add more and more foam to the front of my TC to support the nose of the body and keep it from rubbing Ive come up with a solution. The new bumper has 3 extensions built into the bumper that fully support the nose of the body at 3 points and keep it from dragging the track allowing you to run the body lower in the front. They are desinged to fit the Xray perfectly. They also fit the Awesomatix, TC7 and Gizmo cars although some minor trimming may be required around the back edge where it mounts to the hard bumper. They are designed to have the body mounted 6mm forward if you mount it right up against the bumper taking out a lot of guess work as to how far forward to mount your body for maximum steering and performance. There are two versions. A solid foam version and a Cut out foam version. The solid one weighs in at 5.15grams. The Cut bumper weighs in at 4.25 grams. The stock soft Xray foam bumper weighs 4 grams. These are made from a lot more dense foam than the stock bumper but still light weight. More weight in the front (super heavy bumpers) will take away steering on the racetrack!