Soffit Chutes, Attic Chute, and Attic Ventilation Chute are what I know them as. These 'chutes' are used when you have soffit vents installed in conjunction with a ridge vent. This is necessary when you're insulating a roof. The chutes allow air to flow into the soffit vent where it travels under the roof (over the chute), thus, cooling the roof, and flow out the ridge vent.
If you want to get a look-see at them, any insulation retailer should stock them. (It's their business.) They can be found in the Yellow Pages under INSULATION CONTRACTORS - COLD & HEAT as well as INSULATION CONTRACTORS - EQUIPMENT AND SUPPLIES. When they're installed, make sure the installer insulates at the top-plate so the incoming air doesn't travel down the walls. Otherwise, you'll have a really cold house in winter and you'll run up your heating bill too.