What are /r/ninjawarrior's favorite Products & Services?

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I used lacrosse balls with eye bolts, held together with a washer and two nuts on the end. The balls wear out over time, but for the price compared to official gear you can keep replacing them every year. Also, it's easier to drill through them if you put them in the freezer overnight first.

You can also use bolts with open-ended hooks on the end to create canonballs that you can carry from one hook to another, as opposed to keeping them in stationary positions.

For rings I have these from Amazon: https://www.amazon.com/gp/product/B01KHPSVN0. They've been outside in midwest weather for about a year and a half now, and they seem to be like new still.

You're going to need to do periodic inspections to make sure everything is safe and secure. That's just the nature of having an outdoor gym. Also, I'd recommend zip-tying some pool noodles to the support timbers if you have kids. Crashing into the corners can be quite painful, and these really help. Just cut them down the middle and attach them to any timbers that are in the swing zone.