I wrote a response to someone’s post in regards to HPA basics. I spent so much time in it and went so in depth that I think it deserves its own thread. Feel free to add anything that I forgot to mention. If you are going to get into HPA (High Pressure Air) Airsoft guns, you will always need a tank, line, reg, and engine (except Tippmanns and GBB conversions, they are different) Tank: You have a choice of a 3000 psi aluminum tank or a 4500 psi carbon fiber tank. The difference between a 4500 and a 3000 is that the 4500 is lighter, but it costs more than a 3000. A 4500 costs about $150-ish. A 3000 costs about $50-ish. All prices are depending on deals and if you can find a starter kit. There is also a choice between SLP and Non-SLP. SLP vs Non-SLP: SLP means super low pressure. The output of a regular (non-SLP) paintball tank is about 800 psi. The output of a SLP tank is 300 psi. This comes into play when choosing a reg. Reg: A regulator (or reg as short hand) limits the amount of air that the engine gets, generally from 60 psi to 180 psi, sometimes it is as low as 120 psi, but it is all dependent on the reg. There is something to note, there are 2 different kinds of regs, SLP and Non-SLP. Your SLP regs are going to be cheaper, about $45-$60. However, they can only be used on SLP tanks, which limit what you can get and generally perform worse than Non-SLP regs when paired up with a SLP tank. Also, SLP tanks are falling out of popularity. Non-SLP regs are more expensive, about $110-$160. However, they can be used with ANY tank. Also, they are regarded with being of higher quality and lasting longer, but I can9t attest to that. Line: This is what connects a reg, which is connected to a tank, to your engine (or gun). It usually is a quick disconnect. Many companies make lines and they range from $30-$60. You will most likely get an Amped Airsoft line (good company) for $35. Order it when you get your reg, there many be an option to get it with your reg. I would just order from Amped themselves for your tank, line, and reg. Engine: This would be your gun essentially. You can have a Wolverine, Polarstar, Valken V12, or any other HPA engine that you can find. Some are drop ins and some are complete guns. It all depends on what you are buying or building. My advice, if you are new, buy one or have someone help you build one. If you are experienced enough, build it, it’s a lot cheaper. Engines usually have a line running from it (commonly known as an IGL, internal grip line), so you can connect the line from your reg. Sometimes, the engine will come with one already installed, or you can buy an aftermarket one for abut $10-$25, depending on the engine you choose. If you go with the stock option, you need a qd connector, which should come with your line if you buy it new. Tippmanns: If you do get a tippmann, like I did for my first HPA experience, you’re in for a trip. The entire tippmann system is built into the gun. Every part has something to do with the operation of the gun. It is easy to service and is a ok beginner HPA gun due to its price, equipment needed, and part support (as long as tippmann as a company does not fold, which I think they had). The differences between any other HPA engine and Tippmanns are you can’t use a regulator or an SLP tank, the tippmann is fully mechanical (excluding the omega), and the only AEG parts you can use in a tippmann are the inner barrel and the bucking. You need to use a regular tank and a side check. A side check comes with a line attached. This allows for 800psi to run right into the gun and the gun regulates the pressure itself. If 300 psi runs into the gun, there would not be enough pressure to allow the gun to function. A side check runs between $35-$60. All adjustments (rof and fps) are done internally. Therefore, you need to buy a special pin in order to tournament lock it. Also, in order to adjust anything, all air must be removed from the system, which means the airline has to be disconnected. If the line does not have a qd (quick disconnect), which they usually don’t, you have to turn off the side check and shoot all the air out of the line to disconnect it since there is so much pressure in it. Lastly, for internals, the HopUps in the Tippmanns are generally crap and a TDC mod has to be done, which will cost extra. You can use whatever bucking and inner barrel you can’t, but any inner barrel should be changed from stock because the stock inner barrel for Tippmanns are the cheapest they could get. What are you expecting from a $400 HPA gun. GBB conversions: If you do this, you either hate your life, you live in the north east, or both. In order to do this, you have to add a custom HPA tap to each mag you own. Generally, a tap will cost $12-$15, but the real cost is the mag. What I’ve done and what is recommended, if you want to run a GBB in HPA, use a drum mag. This is because every time you reload, you need to disconnect and reconnect your line. If you already own a GBB, this is a cheap option for getting into HPA, but yo still need a line, tank, and reg, and you need to balance your pressure. You need enough pressure to cycle the gun while being under the fps limit. For many guns, this is a balancing act where the refresh rate after a rapid fire will cause issues if your psi is too low. If you are running a Co2 conversion, you don’t have to worry about this that much since you are already running a high pressure, but it will cost a lot more since you have to get an Ant Kit, $50, and you are not benefiting as much unless you get a tapped Airsoft mag ($120). Total costs: For a tank, line, and reg, the cheapest you can get away with is about $140 on Amped’s website. That is an SLP tank and reg. I have a $300 rig with a 4500 tank, Redline mini SFR reg, and an amped line. For a regular HPA gun (polarstar, Wolverine, etc), it will cost you about $550- $1000+ (depending on what you want or can build). I just built a SR25 Kythera build for about $550 from scratch before attachments. It depends on what you find and it’s cost. However, Tippmanns, new, are $400, and a side check and tank are about $75-$90 total. If you want to get in cheap, go tippmann. If you want to get in the right way, get a polarstar, Wolverine, redline, etc.