3-Ply hose

3-ply hose is processed as it's name, 3-layer tube:  an inner PU tube, a reinforcement jacket, and outer PU tube. There is adhesion to combine those 3-layer together. Adhesion melt during the manufacturing process, and combined the tube and jacket layer by chemical bond, called vulcanization. 

The manufacturing process of 3-Ply starts by pulling a polyurethane (PU) tube though the inside an adhesive tube; then, pulling these two tubes through the inside a woven reinforcement jacket. Steam is blown through the PU tube to melt the adhesive and bond the PU tube to the reinforcement jacket. The tube inside the jacket is then turned inside-out ("turning the inside tube out") and the process is repeated with a second PU tube and a second adhesive tube. During this procedure, moisture builds up on the reinforcement jacket and numerous pin holes are made in the outer PU tube to permit this moisture to escape.

Pros:  cost less, light weight, tube thickness more even, less expension

Through-the-weave

The manufacturing process for extruded-through-the-weave (TTW) hose uses two polyurethane tubes separated by a reinforcement jacket. The PU tubes are extruded through the weave of the reinforcement jacket, melding all components into a single piece of reinforced TPU lay flat hose.

Pros:  inner smooth,  less elongation, more durable