I'm Joanna sun from hengshui China guangxing screen Co.ltd 

A double layer of high performance screen, having a very accurate V-shaped wire welded to support rods
A slot opening for the outer screen, which is selected to retain the formation sand, and an inner screen to retain the gravel pack.
A performance pipe with a variable annulus, which allows installation into very deep and specific wells, for example deviated, horizontal or depleted.
A variable thickness layer of calibrated sand, either with or without epoxy resin, which is contained within the annulus of two concentric screens.
Close control of slot tolerances, designed to prevent sand migration
Better screen protection due to specially designed rings that shield the filtration zone.
Dimensions

As standard, 304 stainless steel is used in the manufacture of the jacket, and J55 or K55 for the pipe base.

The standard external screen open area is 21%, although other percentage open areas are available.