I bought 10 sets from Walmart in 2019 for $3 each. The small hole in the base is for a tether. They'll disappear into the grass if let them. If that happens don't worry, you can easily locate them with your lawn mower.
I have several sets of those. They are able to handle hits from my .22 HW50 with no problem. That is about 11fpe and I’m shooting them at only 13 yards. They are a lot of fun in my little backyard range. At that low price I have accumulated 6 sets of them. They make a great “tink” sound a fly about when hit; even with my HW30 in .177.