Bumper mounts under the chassis with 4 screws.
Most of the Pro bumpers are made of thinner nylon 0.096" to keep the weight down for the 2wd buggies.
The Racer2 for the B5 will also fit the B4.
This listing comes with the following for Associated B5 rear motor:
  • One TBR Pro Front bumper 
  • Lifetime warranty

11140 - TBR Pro Front Bumper -- Associated B5 (Rear Motor)

  • Price $9.99
  • MSRP MSRP $11.99