Peak Design. For an A1 I'd use a Leash as it's light, small & strong. I do have the more robust Slide for heavier/MF cameras (Hasselblad, RB67 etc) but I tend to use the leash for almost everything else. If you're intending to spend a day with it, perhaps the Slide might be better as the wider strap is more comfortable over long periods but for something like an A1 it's probably overkill. As someone with a lot of film cameras it's very handy to put quick release buttons on all of them and just have the 2 straps. Well, 3 if you count the cuff which is also great.