The Adshrink.it shortener was added, the reason is because it pays twice as much as Ouo.io.
It’s also easier to use than Ouo.io, although I know some people prefer Ouo.io because it doesn’t have AntiAdblock and they have trouble turning it off when using Adshrink.it . I will keep both shorteners, although if you want to contribute more I would prefer that you download the Adshrink.it shortener.
Both shorteners count only up to 2 IP visits per day. So the most optimal for me would be if you download many Sets:
2 Adshrink.it + 2 Ouo.io + ∞ any option