What is the most important material we need when build or repair a cylinder?

When building or repairing a hydraulic cylinder or pneumatic cylinder, what is the most important material we need to use? Of course it is honed tube and usually honed tube is ready to use for hydraulic and pneumatic cylinder applications without further inside diameter processing. 

Honed cylinder tube usually is manufactured by two main processing methods, which are honing or skiving & roller burnishing methods, from our "Suitable for Honing" Cold Drawn Seamless Pipes. The manufacturing method of the honed tube is determined by sizes, mold available and the request of the client.
Steel Grades:

Carbon steel grades: SAE 1020, SAE 1026, E355, ST52.3 
Stainless steels: 304 /304L, 316 /316L
Size Range:

Different honed tube factories can produce honed cylinder tubing with different size range.

As the leading honed tube manufacturer in China, I know Skyline's factory produce honed tubing in a wide range of metric sizes and imperial sizes.
Inside Diameter 32mm to 600mm; Imperial sizes equally.
Length: Honed cylinder tubes are supplied in fixed length and random lengths, the max. Length our our honed tube is 14 meters.

Honed cylinder tube is mostly applied for making and repairing hydraulic cylinders and pneumatic cylinders, besides the above, honed tubes also can be used in other applications where high precise inside diameter dimension is required and high smoothly inside surface is required.