A harness for Shaft dildos needs an O-ring that fits the dildo's width, because Shaft models range from about 1.4 to 2 inches wide. Get the ring right and the dildo stays upright and secure. Get it wrong and it either won't go through or flops around mid-thrust.
TL;DR: Quick Answer
- Shaft Model J (5.5 to 7.5 inch) is about 1.4 to 1.5 inches wide and fits a standard 1.5 inch O-ring.
- Shaft A, C and N at 8.5 inches and up are 1.75 to 2 inches wide and need a 1.75 or 2 inch ring.
- Easiest answer: a harness with interchangeable O-rings, like the Sportsheets Lush, fits every Shaft.
- Models with balls sit nicely in a harness, because the balls rest below the ring.
Key Takeaways: Shaft Dildo Harness Fit
- Measure the shaft, not the base: the ring sits around the shaft, just above the base.
- Snug is good: the ring should hold the base firmly without being a fight to push through.
- Bigger Shafts are heavier: 9.5 and 10.5 inch models need a sturdy harness with good support.
- Stretchy rings help: silicone or stretch rings cover a wider range of sizes.
- Clean both: wash the dildo after every use and the harness when needed.
Why the Right Harness for Shaft Dildos Matters
Shaft dildos are made from dual density liquid silicone with a firm core, so they stay upright in a harness. That only works if the O-ring grips the base properly.
A ring that's too small won't let the shaft through. A ring that's too big lets the dildo tilt and wobble, which makes it hard to control your angle and depth.
Already picked your Shaft? Our guide to Shaft dildos for strap-ons and pegging covers which model and size to choose. This guide is about the harness side.
Harness for Shaft Dildos: O-Ring Size Chart
Widths below are the widest diameter from the Shaft listings. Use them to pick your O-ring size.
- Model J 5.5 inch: about 1.38 in wide. Fits a 1.5 inch ring.
- Model J 6.5 inch: about 1.44 in wide. Fits a 1.5 inch ring.
- Model J 7.5 inch: about 1.51 in wide. Snug in 1.5 inch, easy in 1.75 inch.
- Models A, C and N 7.5 inch: about 1.63 in wide. Use a 1.75 inch ring.
- Models A, C and N 8.5 inch: about 1.75 to 1.79 in wide. Use a 1.75 or 2 inch ring.
- Models A, C and N 9.5 inch: about 1.86 to 1.98 in wide. Use a 2 inch ring.
- Model A 10.5 inch: about 1.95 in wide. Use a 2 inch ring and a supportive harness.
For context, the average erect penis is about 4.6 inches around, which is roughly 1.46 inches wide. So the Model J sizes feel close to average, while the 9.5 and 10.5 inch models are well above it.
Best Harness for Shaft Dildos (In Stock Now)
Each harness for Shaft dildos below is in stock and lists its ring sizes. See every option in our harnesses collection.
Best Overall: Fits Every Shaft
Sportsheets Lush Strap On
3 O-rings: 1.5, 1.75 and 2 inch
Comes with three interchangeable rings, so it fits every Shaft model from the J 5.5 up to the 10.5. Our top pick.
Sportsheets Plus Size Beginners Strap On
3 O-rings: 1.5, 1.75 and 2 inch | plus size
The same three-ring setup in a plus size fit. A great pick if standard harnesses run small on you.
Best for Shaft Model J
Get Lucky Strap On Harness
1.5 inch O-ring
A simple, comfortable harness with a single 1.5 inch ring. Perfect for the slimmer Model J sizes.
Best for Big Shafts (9.5 and 10.5 Inch)
All American Whoppers Universal Harness
Metal rings: 2 and 2.5 inch
Two sturdy metal rings, so the biggest Shafts sit secure without stretching the ring.
Best Underwear-Style Harness
Spareparts Tomboi Briefs Harness
Stretch O-ring: 1.25 to 2.25 inch | size M
Looks and wears like underwear. The stretchy ring covers every Shaft size. Other sizes are available too.
Shaft Dildos to Pair With Your Harness
New to strap-ons? Start smaller than you think. Here are three in-stock Shafts that work well in a harness.
Shaft Model J 6.5 Inch
About 1.44 in wide | fits a 1.5 inch ring
Slim and realistic. A great first strap-on or pegging size.
Shaft Model N 7.5 Inch
About 1.63 in wide | fits a 1.75 inch ring
A step up with balls, which help it sit nicely in the harness.
Shaft Model A 8.5 Inch
About 1.77 in wide | fits a 1.75 or 2 inch ring
For confident couples who want more length and fullness.
See every size and color in our Shaft dildos collection.
How to Fit a Shaft Dildo Into a Harness
- Pick the ring. Use the chart above, or test the rings that came with your harness.
- Push the shaft through from behind. The base should stop at the ring with the balls (if it has them) underneath.
- Tighten the straps. Snug enough that the dildo doesn't sag, but not digging in.
- Check the angle. Wearing the harness higher or lower changes where the dildo points.
- Lube up. Use a water-based lube, since silicone lube can damage silicone toys.
For pegging, go slow and use plenty of lube. The Cleveland Clinic notes that anal tissue is delicate and needs added lubrication, so a thick water-based gel from our lube collection is a good idea.
Frequently Asked Questions
Will a Shaft dildo fit any harness?
Most standard O-ring harnesses work, as long as the ring matches the dildo's width. Model J fits a 1.5 inch ring, while the bigger A, C and N sizes need 1.75 to 2 inches.
What size O-ring do I need for a Shaft Model A 9.5?
A 2 inch ring. The 9.5 inch Model A is about 1.98 inches wide at its widest point.
Are Shaft dildos with balls better for harness play?
Many people prefer them. The balls sit below the ring and add stability, so the dildo is less likely to slip forward.
Do Shaft dildos work with Vac-U-Lock harnesses?
Shaft dildos use a suction cup base, not a Vac-U-Lock plug, so use a standard O-ring harness instead.
Which Shaft is best for a first strap-on?
The Model J 5.5 or 6.5 inch. They're slim, realistic and fit a standard 1.5 inch ring. See our Shaft dildos size guide for more help.