They're not cool. They're fast and good for giving lots of shots in a situation where you need to get a lot of people in a hurry - especially if you're giving multiple vaccinations at the same time.

I got one of those used on me in basic training - a place where you need to vaccinate a few thousand people in about 30 minutes. Each one could do 4 shots at a time, and they had them in multiple configurations so you could get up to 4 in each arm for each "injection" station. We stepped through the line, and you got whatever shots you were missing in your records.

It hurts, like you could imagine a high pressure power washer with a needle-point burst with 4 heads blasting vaccines in your arms. It works, in the machine-like way the military works, and it is highly effective for mass vaccinations. So, I guess it makes it cool, but also it sucks like you'd expect 4-30 vaccines at once would suck.