... That's the size of the socket I use, to remove and reinstall the training wheels on Mackie's bike. I've got it down - like a pit-stop!
I got her the bike for five bucks on the Craigslist last March. And that's when the photo was taken. I invested a bit of labor in cleaning it up, greasing the bearings, and I bought $15 worth of new rubber. The previous owner had worn the old tires down to the cord. (Good for her!) We also upgraded her helmet, to a pretty pink-and-green one that she really likes to wear.
Mackie still does a lot of riding with the training wheels, but 'most every session, I take 'em off and we practice the 2-wheelin'.
Early on, she insisted, "I can't do it!" And each time she got a little wobbly, she'd say "See? See?!" as if to reinforce the notion that she can't do it. But that's changed... now I'm barely involved other than walking alongside. And she giggles like a three-year-old! (Can anything be more satisfying to a tired old grandpa?)
I suspect that around Independence Day, the training wheels will come off, and stay off.