Round Base T-nuts
Stainless Steel T-nuts are available upon request. (.60 each)
SS t-nuts are not really necessary unless your climbing wall is exposed to salt water or is near an ocean.
We recently conducted a 2 year experiment comparing Stainless Bolts coupled with Stainless T-nuts to Stainless Bolts coupled with Zinc Plated T-nuts.
We soaked them in water, let it dry up, soaked them again, over and over.
Both combinations had insignificant corrosion. The SS T-nut & Bolt did no better than the Zinc plated T-nut.
The main difference we found was the SS T-nut combo tended to lock up more with or without corrosion.
This makes perfect sense because the Friction Coefficient of Stainless Steel is much higher than alloy steel.
For 99% of the outdoor climbing walls your best setup is Stainless Steel Bolts Coupled with Zinc Plated T-nuts.
If you order bolt on climbing holds and select "Outdoor Hardware" you'll receive SS bolts and Zinc Plated 4 Prong T-nuts.
If you prefer to use SS t-nuts make sure you lubricate the threads of the bolts before tightening them down.