Do I need clamps for this hose?

Yes. This hose ships bare — you'll need worm-gear or spring clamps sized for 2.50" and 2.75" barbed fittings on each end. Most builders use a matched pair rated for your coolant or boost pressure.

Can I use this on a turbo or supercharger line?

Three-ply silicone is rated for boost applications. Test your system pressure against the hose rating before running it — most 3-ply handles 15+ psi comfortably, but verify your specific setup's requirements.

What's the best way to fit this reducer between two hoses?

Slip the larger end onto the 2.75" diameter fitting first, clamp it down, then slide the smaller end onto your 2.50" line. Tighten both clamps evenly to avoid kinking the transition. A small amount of hose lubricant makes sliding easier without damaging the silicone.