The A5 RIS (Rail Integrated System) will allow you to mount bipods/flashlights/lasers, etc. to the Picatinny rails on the bottom or either side in the front grip area. It includes three Picatinny rails and a new stainless steel shorter stock front grip screw. It is finished in a matte black to match your A-5.
The main differences between the RIS and the RIS MkII is the RIS is taller. This allows additional room for mounting your tactical gear (especially under the cyclone) plus it is hollow to cut down on weight.
The Underground Mod Shop A-5 RIS (Rail Integrated System) is older, so while it may be available used and in a few cases new, it is not commonly available anymore.