Cup vs Hat vs Integrated: Choosing a Structure

The flexspline shape defines how the reducer mounts and where it fits — a quick guide to the three main structural families.

Cup-type (standard & short)

In a cup-type reducer the flexspline is shaped like a cup; the rigid circular spline is usually fixed and the cup end outputs. Cup types are compact, light and easy to seal, and the short cup variant trims axial length further for very tight spaces while keeping torque capacity.

Hat-type (standard & short)

Hat-type units use a hollow, flanged flexspline. The flange gives a large mounting surface and the hollow bore lets cables or a through-shaft pass through the center — ideal for robot wrists and axes that need center routing. Short hat variants reduce height for low-profile joints.

Integrated (built-in bearing flange)

Integrated units build the support bearing and flange into the reducer, so the motor can often be mounted directly and the assembly is ready to use out of the box. This simplifies design, shortens the drive chain and improves stiffness — at a small premium in size and cost.