Which coupler size and class is right for towing my boat trailer safely?

What Is a Coupler Class Rating?

A coupler class rating is the weight capacity and hitch ball size your boat trailer coupler is designed to handle. The coupler is the latch mechanism on the trailer tongue that locks over the tow vehicle’s hitch ball.

Each class rating corresponds to a maximum Gross Trailer Weight (GTW) and a required ball size:

• Class I (up to 2,000 lbs) – usually 1-7/8″ ball, very small trailers/PWC.
• Class II (up to 3,500 lbs) – 1-7/8″ or 2″ ball, light single-axle boat trailers.
• Class III (up to 5,000 lbs) – 2″ ball, common for most mid-size boat trailers.
• Class IV (up to 10,000 lbs) – 2″ or 2-5/16″ ball, used on larger tandem or tri-axle trailers.
• Class V (10,000–12,500+ lbs) – 2-5/16″ ball, heavy-duty triple-axle offshore boat trailers.

To determine what coupler you need:

1. Check your trailer’s GVWR (Gross Vehicle Weight Rating). The coupler must meet or exceed it.
2. Match the ball size listed on the coupler to your tow vehicle’s hitch ball.
3. Read the stamping on the coupler—it specifies both GTW rating and ball diameter.

⚠️ Using the wrong class rating or ball size risks unsafe towing, coupler failure, or trailer detachment.