A tow ball is the steel ball your trailer's coupling locks onto, and a tow ball mount (also called a tongue or drop hitch) is the bar that holds the tow ball and slides into your towbar's square hitch receiver. Together they set how much you can tow, how high the trailer sits and how securely it's connected, so both need to be the right size and rating for your setup.
This guide covers tow ball sizes and ratings in Australia, the main types of tow ball mounts, extended mounts and hitch extenders, and how to fit a tow ball correctly.
Tow Ball Sizes in Australia
There are two tow ball sizes you'll see on Australian towbars:
- 50mm tow ball: the standard size for trailers, boats and caravans up to 3500kg. It's what almost every Australian trailer coupling is made for.
- 70mm tow ball: used for heavy towing above 3500kg, on vehicles, towbars and hitches rated for it. It needs a trailer with a matching 70mm coupling.
Every compliant tow ball is stamped with its ball size and its maximum rating. Use a ball rated at or above your trailer's loaded weight, and remember your real limit is the lowest rating anywhere in your setup.
| Tow ball | Rating | Shank | Torque spec |
|---|---|---|---|
| TAG 50mm zinc plated | 3500kg | 7/8" (22mm), 62mm long | 300Nm |
| TAG 50mm chrome | 3500kg | 7/8" (22mm), 62mm long | 300Nm |
| TAG 70mm chrome | 4500kg | 1-1/4" (32mm), 62mm thread | 750Nm |
Shank size and the reducer bush
The shank is the threaded stem that bolts through the tow ball mount. 50mm tow balls commonly use a 7/8" (22mm) shank, while 70mm balls use a thicker 1-1/4" (32mm) shank. If your mount is drilled for a 70mm ball but you want to run a 50mm ball, a 32mm to 22mm reducer bush fills the gap. Never fit a ball whose shank is loose in the mount's hole without the correct bush.
Types of Tow Balls
- Zinc plated: a hard-wearing, low-cost finish that's easy to keep greased.
- Chrome: the same strength with a brighter, more corrosion-resistant finish.
- Shock-absorbing: the CURT RockerBall has a built-in cushion that reduces jerking and rattling between your vehicle and trailer.
- Swan neck (integrated): on European swan neck towbars the ball is part of the neck, not a separate bolt-on ball. See Towbar Types Explained.
Tow Ball Mounts Explained
A tow ball mount sets where your tow ball sits. When comparing mounts, check five things:
- Receiver size: most Australian towbars use a 50mm square hitch receiver, but some lighter towbars use 40mm. A 40mm mount won't fit a 50mm receiver, and vice versa.
- Rating: mounts are rated for a maximum trailer weight and ball weight, and these vary a lot (see the table below).
- Drop or rise: how far the ball sits below or above the receiver. Most mounts can be flipped to use as either a drop or a rise.
- Length: measured from the hitch pin hole to the tow ball hole. Longer mounts give more clearance from the rear bumper or spare wheel but add leverage.
- Tongue face angle: TAG mounts come with 90°, 108° or 135° faces. Choose the one listed for your towbar or the one that gives you a level trailer.
| Example TAG mount | Receiver | Drop/rise | Max trailer / ball weight |
|---|---|---|---|
| 220mm, 135° face | 40mm | 0mm | 1600kg / 160kg |
| 203mm, 90° face | 50mm | 70mm | 2500kg / 250kg |
| Adjustable heavy duty | 50mm | Up to 115mm, adjustable | 3500kg / 350kg (50mm ball), 4500kg / 450kg (70mm ball) |
| 4" drop forged | 50mm | 100mm | 4500kg / 450kg |
As the table shows, two mounts that look similar can have very different ratings, so always check the rating before you tow a heavy trailer. Browse our full range of tow ball mounts and hitches.
Fixed, adjustable and forged mounts
- Fixed mounts have one drop/rise and are the simplest, lowest cost option.
- Adjustable mounts let you move the ball up or down to suit different trailers, or a lifted 4x4 that needs a big drop.
- Forged mounts are made from a single piece of steel for higher ratings, like the 4" drop forged mount rated to 4500kg.
- Cushioned mounts such as the CURT Rebellion XD ShockDrop add a built-in isolator to absorb shock between the vehicle and trailer.
Extended Tow Balls and Hitch Extenders
If your tow ball sits too close to the bumper or rear-mounted spare wheel, the safe fix is a longer tow ball mount that's rated for towing, not an extension.
- Hitch extenders are not for towing. Products like the TAG hitch extender are designed to move a bike rack or carrier further back, not to tow a trailer.
- Dual-use mounts like the TAG Dual Use Tow Ball Mount have a lower receiver for towing (rated 2700kg / 270kg) and an upper receiver for a bike rack or carrier only.
- Length adds leverage. Every extra centimetre between the receiver and the ball increases the load on the towbar, which is why longer mounts can carry lower ratings. Never stack extensions or adapters to gain length.
How to Fit a Tow Ball
- Check the ball's size and rating stamp match your trailer coupling and load.
- Make sure the shank suits the hole in your mount, using a reducer bush if the mount is drilled for a larger ball.
- Clean the threads and the mount's face so the ball seats flat.
- Fit the ball through the mount and fit the nut and washer supplied.
- Tighten the nut to the ball manufacturer's torque spec with a torque wrench: 300Nm for TAG 50mm balls and 750Nm for the TAG 70mm ball.
- Slide the mount into the receiver, fit the hitch pin and R-clip, or use a locking hitch pin.
- Re-check the ball nut's torque after your first trip and regularly after that.
Lightly grease the ball for a standard coupling to reduce wear, unless you're using a friction-type sway control that needs a clean, dry ball.
Checking Your Tow Ball Weight
Tow ball weight (or download) is the downward weight your loaded trailer puts on the ball. Too little can make a trailer sway; too much overloads the rear of the vehicle. A commonly used guide is around 10% of the trailer's loaded weight, but it must stay within the lowest ball weight rating in your setup. A TAG tow ball weight scale lets you check it at home before a trip.
Tow Ball FAQs
What size tow ball is standard in Australia?
50mm is the standard tow ball size in Australia, used on trailers and caravans up to 3500kg. 70mm tow balls are used for heavier towing above 3500kg with a matching coupling.
What is a 70mm tow ball used for?
A 70mm tow ball is used for towing above 3500kg, such as 4500kg towing on vehicles, towbars and hitches rated for it. The trailer must have a matching 70mm coupling.
Can I use an extension to move my tow ball further back?
Not a hitch extender. Extenders are designed for bike racks and carriers, not towing. Use a longer tow ball mount that is rated for towing your trailer instead.
How tight should a tow ball be?
Tighten the tow ball nut to the manufacturer's torque specification with a torque wrench. For TAG tow balls that's 300Nm for the 50mm ball and 750Nm for the 70mm ball. Re-check it after your first trip.
Is a tow ball the same as a towbar?
No. The towbar is the frame bolted to your vehicle. The tow ball sits on a tow ball mount that slides into the towbar's receiver, and it's the part the trailer coupling locks onto.
Shop tow ball mounts and hitches and towing accessories, or contact us if you're not sure which tow ball or mount suits your towbar.