I've never swapped cranks or a bottom bracket before, but I've done just about everything else on my 1x1. I just started riding it fixed with 175mm cranks and I realized that I really need shorter ones.

So now I'm trying to sort this all out and I don't really know what specs to look for to find both a bottom bracket and crank to fit my 1x1. I found Gravity Maximus-2 Crank Arms that look beefy and are the right length. According to the site I found them on they need an ISIS interface bottom bracket.

So what sized bottom bracket do I need? I found several ISIS BB's but I don't fully understand what the 108, 113, 118mm sizing means.

Any recommendations would be much appreciated in terms of sizes, brands or just what in general I need to make this fit on my 1x1.

Thanks in advance everyone.