Scottydogs recommended to me to use band clamps and thst's what I'm using. There are ones that are tapered for like 3" - 2.5" piping, or the ones that are just straight 3" / 2.5". I used the ones that aren't tapered and I have no leaks at my bandclamped connections. But my flexpipe does leak quite a bit on my roughly 8k miles old SD's. Kind of annoying and I wish I had that piece replaced when I had them off the car. Hindsight lol