S400 GRP Heavy Duty Trade Step Ladder - 6 Tread (EN131) Description Offering a long lifespan and excellent build quality, the aluminium and fibreglass (GRP) Catwalk S400 is designed to withstand heavy trade use and is non-conductive to 30,000 volts. Features Tested and certified to EN 131. Treads are double riveted for extra strength. Integral tool rack. Slip-resistant treads and feet. Braces for extra rigidity. Available in 4, 6 or 8 treads - 8 tread has a maximum safe working height of 3.132m.