Preferred models include DOUBLE FOOT BOARDS on all rows for added safety Tip N' Roll bleachersare perfect for auxiliary seating requirements. Unit easily tips up on its casters for convenient storage. Framesare 100%welded aluminum angle Seat planks are either anodized or powder coated (where applicable) High grade swivel casters & rubber foot pads will not mar your floors Due to constantly changing specifications, please check local building and safety codes to insure compliance. 4 row models feature low rise framework - the first seating row is 12" off the ground. Some assembly required WARNING: These lightweight units are easily tipped up for rolling by any responsible adult. However, if tipped up outdoors, extreme caution should be taken in windy conditions. Multiple adults may be required to control the unit.