Will this hose work for coolant circulation, or is it better for vacuum lines?

Silicone hose of this grade handles both coolant and vacuum applications. What matters is matching your system's operating temperature and pressure range to the hose spec — get that right and you're good either way.

Do I need hose clamps, and what size should I use?

You'll need clamps to secure the ends, but clamp size depends on your fitting diameter, not the hose itself. Measure your barbed fittings and go up one size for safety — most 4" ID setups use standard worm-gear clamps in the mid-range.

Can I cut this hose shorter, or does it come pre-formed?

Silicone hose cuts clean with a sharp blade or hose cutter — no special tools needed. Pre-form it to your routing, then trim if needed before final clamping.