... Ring or Steel Ring 4.Size, 7"x17" PP/PE needle Felt Filter Bags were made by PP,PE,Nylon,Nomex and Oil ... used in liquid purified with filter bag vesse together. 7"x17" PP/PE needle Felt Filter Bags1).Nominal micron filter bags (#1,#2,#3, ... ) 2).Absolute micron filter bags.(#1,#2,#3, ...