These keel rollers will mount along the center-line of your boat trailer, typically on a Galvanized Roller Bracket and will provide support for your boat to allow easier loading and unloading. Keel Rollers are essential for the trailer, loading, and unloading process. They Support the hull, guide the boat, and furthermore protect it from damage.
These keel rollers are most commonly mounted on the trailers cross-members in front and behind the trailers axles.
As pictured. Each roller has a shaft size of 5/8”