STURDY : Heavy Duty Material and Double Locking Mechanism Ensures kip Bar’s Safety and Security. STRONG: High-strength Fiberglass Bar Rail with Weight Limit Of 330LBS. QUICK：Double ABS Knob for Convenient Assembly. Easy to Assemble with Only 8 ABS Knobs and 10 Screws. ADJUSTABLE: Gymnastics Bar Height Can Be Adjusted from 3’ to 5’ With 10 Height Options. DURABLE: Anti-bending Tie Rods and Stainless Steel Regulating Arm Adds Durability of Horizontal Bar. material type: Aluminum