Boeing 737 Brakes
Reference the difference between the brake units themselves.... You can fit two different brands of unit on the NG (BF Goodrich or Honeywell (Bendix)). This is normally detrmined at the time of purchase of the aircraft. There are then two different versions of each manufacturers' brake unit dubbed "Standard" and "High Capacity". So, for a 737-700 (assumed MTOW of 155k lbs) you can have a "Standard" BFG brake unit, which is classified as a Cat B Brake. The Honeywell "Standard" unit is classified as a Cat A brake. The High Capacity units for both Manufacturers are Cat F brakes. Note that on a 737-600 the same part number brake units are rated as Cat E, Cat D and Cat D respectively.....
Boeing offers (for a price) non mandatory Service Bulletins which allow an upgrade of Brake units either in change of Manufacturer or between Standard and High Capacity. The Wheels also have to change so it is an expensive business. More details are to be found in Service Letter SL-737-32-101.