STEP LIP configuration is stronger and reduces weight in comparison to reverse configuration (flat lip) wheels. FLAT LIP configurations available in 17€³ sizes and larger with custom widths. STANDARD Backpad Pocketing. STANDARD Spoke Beam Contouring. AEROSPACE GRADE 6061-T6 forged aluminum for optimun strength-to-weight-ratio. PRECISION CNC production to your specifications for any custom application. OE TPMS and mounting hardware compatible. ENDLESS FINISHING OPTIONS available in polished and custom powdercoated options, customize your F339 to achieve the specific look you are envisioning.