Spiral / Spiro Metal Duct for HVAC
It is a spiral duct which can is commonly used for HVAC.

The color, amount of polished lines, amount of scratches, dirt level etc. can be changed by using the Substance SBSAR file.
 
Flexible Metal Duct Texture
It is an elastic duct made of aluminium foil and some metallic rings. The crumpled texture offers the flexibility for bending. Therefore, this kind of ducts is usually used as a gas pipe.

The color of the foil and metal rings can be changed by the Substance SBSAR file.
Flexible Plastic Electrical Conduit / Duct
It is a flexible plastic conduit for housing electrical or LAN cables to tidy up the wiring.

The color, level of distortion, amount of dirt etc. can be managed through the SBSAR file.
 
Air Duct Rubber Texture
It is a black rubber which has a little foam-like texture. It can be used for texturing wrapping air pipes or car tires.

The SBSAR file allows users to change the color and tweak the imperfection of the surface.
Glossy Brown Duct Tape Texture
This is a brown duct tape having a glossy texture. They are those used to close openings of cartons.

It is common that boxes are full of brown duct tapes.

Due to large surface area, duct tapes usually have a lot of wrinkles or folds that can be found on this texture.

If you are planning to create a carton box 3D model, you may want to consider Caution Labels for Carton Boxes (Decals 0007) and Carton Box Cardboard Texture (Paper 0025).