Steel conduit weighs more, provides more protection, and costs more than plastic conduit. Plastic conduit weighs less, is easier to work with, and costs less than steel conduit.
One can find information about conduit fittings from various sources. Some of those sources are Grainger, Home Depot, Prime Conduit, Steel Conduit and Lowes.
In the true definition of a conduit yes a steel sleeve is in that category.
The prices of PVC conduit seem to be a bit cheaper than steel conduit. PVC is light and lower in cost to produce and manufacture. Depending on the place that the conduit is needed, can determine the type of conduit you need.
Conduit is piping for electrical wiring. Steel conduit is the most common conduit used. It is often left visible in industrial atmospheres and can be seen running to electrical outlets, lighting panels, electrical panels, etc.
steel and plastic conduits
There are many types of conduit used for the containment of electrical wires. PVC is a non-metallic option. If you need something that provides mechanical protection, EMT is a steel conduit with a thin wall. Need even more mechanical protection, you can use rigid conduit. It comes in steel or aluminum, and must be threaded together.
it is stronger and live for a long time
In electrical terms it represents Rigid Steel Conduit. It is also known as Rigid Metal Conduit (RMC).This is not to be confused with Electrical Metallic Tubing (EMT) also known in the trade as thin wall conduit.
Heavy wall threaded conduit comes in steel or aluminium. The aluminium conduit is NOT galvanized because you can not galvanize aluminium. Steel conduit used to come in two types: ENAMEL and GALVANIZED. The ENAMEL was not approved for outdoor or wet locations and is not currently generally commercially available but is still found in many existing buildings. It is NOT galvanized. The GALVANIZED type is approved for all locations.
One can buy Steel-Craft door products in the official Steel-Craft website online or in near Steel-Craft stores. Also, other retail stores can provide Steel-Craft door products.
In the first part of the question there will be only one wire in the conduit, in the second part of the question there will be two wires in the conduit.