Rule R404

R404 *BUMPERS must be soft. Hard parts of BUMPERS must not extend more than 1 ¼ in. (~31 mm) from the ROBOT PERIMETER. Only padding (per R402-A), cover (per R402-C, including any coatings or markings), and soft fasteners used to secure padding or cover are permitted beyond this limit. Padding must extend at least 2 in. (~51 mm) beyond any hard parts of the BUMPER.

Hard parts include any items which are likely to cause damage to the cloth or padding of other BUMPERS such as nuts and bolts, cable ties, hard plastics, etc.