The J&L oil separator for the 99-13 GM truck (Silverado, Sierra, Yukon, Tahoe, etc.) application bolts to the side of the alternator bracket using one of the alternator junction box bolts. This catch can is available in black anodized or clear anodized (silver) finish. The GM truck PCV systems are notorious for oil consumption through the intake. The addition of a catch can helps to limit the amount of oil vapor the can reach the intake manifold which helps to keep the intake tract cleaner and free from oil deposits.
Filtering consists of a fine mesh stainless steel screen that traps fine oil vapors and releases them once heavy enough to fall. They then pass through a 1/2" thick 1/16th" aluminum honeycomb filter where they grow larger and then fall into the bottom. By the time the oil gets through the filter it's too heavy to be passed on into the intake. The tank holds 3oz of fluid. Optional tank extension increases capacity to 6oz.
NOTE: Some 2007 and later applications use a quick connect style fitting at the valve cover. This can be removed and the catch can line can be clamped directly to the valve cover barb. If your truck is a 2010-2013 model, a portion of the OEM PCV tube may need to be retained in order to connect the outlet hose of the catch can to the PCV fitting on the top of the intake manifold.