Reddit mentions of Camp Compact Oval Screw Gate Carabi Carabiners 000 Polished

Congratulations on the new rig! I strongly recommend, though, that you consider getting oval non-locking carabiners instead. Those Black Diamond screw-lock HMS carabiners will work, but you will be cross loading them. HMS carabiners are meant to be loaded at the spine and nowhere else, whereas oval carabiners are intended to be loaded at the basket. A slackline will always spread the load out away from the spine.

Also, there's no style of carabiner more convenient to use for a slackline than an oval. When putting tension on the primitive, the ovals naturally center the lines to overlap each other. When I used to rig with HMS's, I found that the lines could slide out from under each other if when I was less attentive to pull direction, which often prevented locking of the tension and multiple grumbling resets.

So far, my favorite biner for primitive is the "Rollerbiner". While most Americans I've talked to don't think they work, Rollerbiners seem to have had great success for Europeans.

Otherwise, Camp Oval carabiners are the next best bet. Camp's biners are just as strong as the next brand, but their oval carabiners don't have that pesky hook nose for the gate. Instead, their ovals have a keygate, which is a significant improvement, aside from convenience, in the safety and longevity of a slackline. Hook-nose carabiners have the tendency to grab, and, in some cases, cut your line, whereas keygate carabiners never have these issues.

*edit: grammar