Don't over-think this. I'm giving this a total 5 star because the pump is really great and very good quality from my experience and works as advertised with my Benjamin Maraurder pistol. But the user manual and the added parts made it confusing at first, but I'm not rating the user manual. I'm new to this whole air rifle thing but I do like learning new things.First, forget all those additional parts and o-rings. They will be of great help one day if you need them but you don't need them right now. Almost forget the user manual but it might be helpful one day too if parts fail or whatever...because of the diagrams. The broken English is either annoying or entertaining depending on your point of view.For the most part, it's ALL almost already assembled - the manual makes you think you need to do more than what you really have to do. All you got to do is attach the handle, the hose and the gauge. That's it. It IS nice to know what engineering goes into the rest of the pump by looking at the diagrams. But that's not necessary to use the pump.Listening to it as I used it, I think just a few drops of oil will help preserve the piston but it works fine out of the box (after the assembly). I know it makes a weird sound when you pump it without anything attached to it. But that's normal and it does work. It can leak in places - just tighten them a little. I've pumped my Maraurder to the 3000 psi level with this pump - it worked fine. The pump also seems to have a kind of black powder coating which is really cool, as opposed to some of the glossy finish I've seen on others.I just realized that they included some cigarette-shaped foam things - two baggies of them - these are for cleaning your barrel. I had no idea what they were for at first. Very nice consideration. Still pumping my Benjamin Maraurder with this pump and it still works great. Thanks for the cleaners!

PCP hand air pumps are NOT easy to use. Not anything against this specific pump but all high pressure hand pumps as a fact of physics. If you don't weigh at least 180lbs, you likely can not fully compress this pump. A 165lb person can put all their weight on the handle and not fully compress it. That said, great value for the money and works as advertised assuming you have enough mASS to use it. Great workout if COVID is keeping you from the gym.Update: Oct 2021. Used the pump to pump up PCP gun about 30 times. Started airlocking where you couldn't fully lift or compress the handle. On teardown, found the 3rd stage piston was trashed and internal port completely plugged with oily, tar like residue and melted o'ring. Photo shows rebuilt 3rd stage piston assembly. Also found there was zero coolant between the 2nd and 3rd stage tubes which is necessary to conduct the heat away from the 3rd stage tube. No doubt, this caused the pump failure. This fluid did not leak out, it was shipped like this. I replaced the o'rings for the top and bottom of the 2nd stage tube and filled the void with antifreeze (greenish fluid in photo). Lubed lightly with silicone airgun lube and reassembled. Working as good or better than new. There were no instructions on teardown, so I improvised. This is how I tore it down. Teardown: General: Use extreme caution not to dent or scratch any pump tubes or brass fittings or you will destroy the pump. All fittings easily unscrew by hand once initial torque is broken free. I reassembled everything firmly hand tight. All pressure seals are o'ring or check valve dependent - not torque dependent.1. Remove handle and cap from top of pump by turning handle CCW and holding 1st stage outer tube with off hand.2. Push cross-pin out of 1st stage brass pump cap. There is a rubber check ball inside the brass cap above the pin. It will fall out when the pin is removed. Rubber ball should be clean and free of old oil and dirt/tar.3. Pumps tube assemblies will unscrew from the pump base. Use a large adjustable wrench or channel lock pliers to loosen and unscrew tubes from base.4. You can access the output check valve by unscrewing the brass plug on the bottom end of the pump tube with a large straight slot screwdriver. There is a conical spring under the plug, pay attention to orientation when you remove it!5. Unscrew 1st stage tube nut from the bottom of the tube and remove the 1st stage tube. You may need the channel lock pliers to loosen it. This gives you access to the 2nd stage cap.6. Hold the pump tubes upright for this step to prevent spilling coolant fluid (if the mfg put any in it) from the chamber under the cap. 2nd stage cap has 2 holes on either side. Removal of this cap allows access to the fluid reservoir and also removal of the pumps 3rd stage rod and piston. You need to insert 2 punches in those holes, grasping the cap and punches turning CCW while holding brass nut on the bottom of the 2nd stage tube with channel lock pliers or wrench. Once the cap is loosened, it comes off easily. The punches give you necessary grip and leverage to loosen the cap without damaging the brass cap. Pliers may damage the cap which would scratch the inside of the 1st stage pump tube and destroy the pump. DON'T DEFORM THE 2ND STAGE PUMP TUBE CAP!7. 3rd stage pump rod and piston will now lift out of the 3rd stage tube.8. The 3rd stage piston, o'ring, brass washer, spring, and slotted cap are on the bottom end of the 3rd stage rod. They all need to be clean and tar/ debris free. Should be very lightly lubricated with silicone pellet gun oil. NOTE: The bottom end of the 3rd stage rod and the slotted cap are hollow with a side port under the piston. This hole and side port must be clear in order to releve the negative pressure in the 3rd stage chamber when you lift the pump handle. If it's obstructed, you will not be able to fully lift the pump handle or likely not be able to fully compress it either. Mine was completely clogged with tarry oil and melted o'ring residue.You should clean all residue and old oil from all orings and check valves, springs, and other components. Qtips and cotton cloth are recommended. Ensure there is no moisture anyplace other than in the coolant chamber between the 2nd and 3rd stage tubes. All o'rings and valves should be very lightly lubricated with silicone pellet gun lubrication fluid before reassembly. They give you several complete rebuild kits, so you shouldn't be at a lack for replacement parts. Good luck!