Lower Part of Office Chair

The lower part of an office chair typically consists of three main components: the chair base, casters, and gas lift cylinder, with some models also including a seat pan. Common styles include five-star bases and bow bases. The following provides an introduction from the perspectives of components and styles:

Components

• Chair Base: As the core component supporting the entire structure, it comes in various materials. Metal (such as steel or aluminum alloy) offers strong load-bearing capacity and durability, nylon is lightweight and quiet, and solid wood is often used in high-end models. The bottom is usually designed as a five-star base (five-claw structure), which enhances stability by distributing forces radially. Surface treatments include polishing, baking paint, or electroplating to prevent rust. Some mid-to-high-end models feature a tilt resistance adjustment knob on the inner side of the chair base, allowing users to adjust the force required for the chair back to recline by rotating the knob.
• Casters: Installed at the ends of the chair base, they come in two types: regular casters and PU wheels. Regular casters are suitable for hard floors, while PU wheels, made of soft materials, are quiet and protect wooden floors. Both types support 360° rotation. The current mainstream design adopts a double-ring silent structure, with a metal axle core wrapped in a soft outer layer, reducing noise and carpet wear. Gaming chairs often add spring-loaded footrests at the bottom of the five-star base to meet the needs of lying down, while high-end ergonomic chairs are equipped with caster locking mechanisms to prevent sliding during work.
• Gas Lift Cylinder (Height Adjustment Cylinder): Located at the center of the chair base, it connects the seat pan to the base and enables height adjustment and rotation of the seat through internal air pressure. Pressing the handle controls the lifting, and some models support 360-degree rotation. To enhance safety, mid-to-high-end products are equipped with an explosion-proof steel plate around the gas lift cylinder to prevent the cylinder from piercing the seat in case of accidental explosion.
• Seat Pan: Connects the gas lift cylinder to the seat and controls functions such as the recline angle. It is usually hidden beneath the seat and not directly exposed. A rotating seat pan combined with height adjustment is commonly found in executive chairs or adjustable office chairs, supporting 360-degree rotation.

Common Styles

• Five-Star Base: Made of metal or nylon, it features a five-claw radial design with universal wheels, offering strong load-bearing capacity and flexible movement. It is widely used in ergonomic chairs and gaming chairs.
• Bow Base: The metal frame is bent into a bow shape and rests directly on the floor without wheels. It has a sturdy structure and is suitable for conference chairs and staff chairs, characterized by simplicity and durability.
• Fixed Wood Base: Made of solid wood with various shapes (such as round or square), it is commonly found in vintage or high-end office chairs. It does not have mobility but offers excellent stability.
• Smart Design Base: In recent years, gravity-sensing brake wheels have become popular, automatically locking when the user stands up to enhance safety. Some high-end models feature spring-loaded footrests or lockable casters to further optimize the user experience.