Per NKA 2022:
20.4.7: Seat Belts 20.4.7.1: Mandatory 5-point minimum harness must be commercially manufactured for motorsports with SFI rating. 2” wide belts are allowed for drivers less than 150 pounds; 3” wide belts are required for drivers over 150 pounds. 20.4.7.2: Lap & Sub Belts Cannot wrap around fame and must be mounted via a welded on steel seatbelt tab: at least .063” thick and 2” square. 20.4.7.3: Shoulder Belts Cannot be mounted to vertical cage rails and must be lower than the driver’s shoulder blades. 20.4.7.4: Arm Restraints Mandatory SFI-rated, must attach to seat belt system, and not allow any part of the driver’s hand or arms outside the cage when fully extended.
In past years belts were dated with a manufacture date and MOST tracks and rule sanction bodies were TWO years past that date. Some tracks would inspect the belts and if they were in good condition (no burns, fraying, etc.) would allow up to five years past the the manufacture date. Today belt manufactures now mark belts with an expiration date (normally two years from the manufacture date). It seems to depend on the track and sanctioning body as to how picky they get. One thing I've never seen enforced is the 2" or 3" wide rule based on driver weight. I'm 215lbs and have ran nothing but 2" everywhere I've been.