CURT Posi-Lock Trailer Couplers: Ball Size, Channel & A-Frame Fit
CURT Posi-Lock couplers use an adjustable spring-and-nut latch to secure the trailer to a matching hitch ball. The six models here include straight-tongue couplers with 2-, 2½- or 3-inch channels, plus a separate A-frame version. Choosing the correct ball diameter, mounting shape and weight rating is more important than matching the appearance of the latch.
Choose the trailer tongue first
2-inch straight channelChoose 25128 for a 1⅞-inch ball with a 2,000 lb GTW rating, or 25153 for a 2-inch ball with a 3,500 lb rating. They cannot share the same ball size.
2½- or 3-inch straight channel25135 fits a 2½-inch-wide straight tongue. 25138 and 25100 both have 3-inch channels for 2-inch balls, but are rated to 3,500 and 5,000 lb GTW respectively.
A-frame tongue25210 uses a 2-inch ball and is rated to 5,000 lb GTW. It mounts to an A-shaped trailer tongue, not over a rectangular straight channel.
CURT Posi-Lock coupler specifications
| Part number | Ball | Mounting size | Max GTW | Max TW |
|---|---|---|---|---|
| 25128 | 1⅞ in | 2 in straight channel | 2,000 lb | 200 lb |
| 25153 | 2 in | 2 in straight channel | 3,500 lb | 500 lb |
| 25135 | 2 in | 2½ in straight channel | 3,500 lb | 500 lb |
| 25138 | 2 in | 3 in straight channel | 3,500 lb | 500 lb |
| 25100 | 2 in | 3 in straight channel | 5,000 lb | 700 lb |
| 25210 | 2 in | A-frame | 5,000 lb | 700 lb |
CURT lists the five straight-channel models with zinc-plated steel bodies, while the A-frame 25210 uses a gloss-black powder coat. All six use Posi-Lock adjustment; their mounting geometry and rating are model-specific.
Check both ratings and every connection. Gross trailer weight (GTW) and tongue weight (TW) are separate limits. A higher-rated coupler does not increase the rated capacity of the trailer, hitch ball, ball mount, vehicle or frame. The hitch ball diameter must match exactly; a 1⅞-inch-ball coupler is not compatible with a 2-inch ball.
Measure these details before ordering
- Identify the frame shape. Measure the actual width of a straight tongue or confirm A-frame geometry. The 25210 is not a substitute for a channel-mounted coupler.
- Read the ball diameter. CURT 25128 is for a 1⅞-inch ball. The other five listed models use a 2-inch ball. Do not interchange them.
- Compare GTW and TW separately. The 25138 and 25100 share a 3-inch channel and 2-inch ball but have different maximum trailer and tongue-weight ratings.
- Verify the latch and safety hardware. Posi-Lock uses spring-and-nut adjustment and has a provision for a safety pin or coupler lock. Check the exact product's supplied parts and correct latch adjustment.
- Follow installation requirements. Confirm tongue condition, mounting locations and approved fastening or welding method for the exact coupler. Have structural trailer modifications performed professionally.
- Check every towing component. Use the lowest-rated component in the system, and follow the tow vehicle and trailer manufacturers' instructions.
Shop exact CURT Posi-Lock couplers
Each card opens the matching CURT manufacturer part number in NewRVParts. Products ship from supplier warehouses; warehouse viewing and pickup are not available.
More trailer connection references
For the rest of the trailer connection, see our CURT safety pins by diameter, DeadBolt coupler lock sizes and Husky trailer couplers. Confirm the specific components independently before combining them.
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