The Tango Down 30-rd and 20-rd ARC Magazines for AR15/M4 Style rifles: A basic problem for plastic magazines is that they have to have a constant curved interior to be molded in one piece. There is no other way. But the magazine well of the M16/AR-15 weapon system is straight. So much compromise has to be reached from a design standpoint to make the two work together. So side effects of magazines not dropping free, are often seen. The optimum solution would be a straight upper section to properly present cartridges through the magazine well, and a constant-radius lower section to accommodate remaining ammunition. However, this design has been impossible to produce in polymer... until now. The patent pending two-piece modular construction allows us to create the ultimate magazine for many reasons. In addition to the proper magazine form, we are able to achieve maximum strength and integrity when the components are molded. Precision molding is achieved much easier on two small parts versus one large one. We can also mix materials, impossible with conventional plastic magazines. We can offer transparent-solid color lowers/high tensile strength upper sectioned magazines that avoid the brittle feed lip issue of all-single material construction. Modular construction makes perfect sense for the unprecedented strength- we eliminated the removable floor plate, so the magazine becomes a five-sided box. ARC Mag survives the impact that crushes metal magazines. ARC Mag takes full advantage of the latest polymers available from the aerospace industry- materials impervious to the effects of solvents & lubricants. After molding, we permanently bond the two sections together with advanced adhesives during manufacturing, so no disassembly is possible, or required. ARC Mag has a unique low-friction semi-floating follower that is slotted to allow for easy magazine cleaning. Just dunk the ARC Mag in hot soapy water, rinse and invert to drain. That's hassle-free maintenance. ARC Mag also features a premium stainless steel spring. Life expectancy for this spring is 100,000+ cycles. -Tango Down TANGO DOWN WEBSITE: http://tangodown.com/shop/index.php?cPath=54&osCsid=c27822249e28236e09d3711318930e5c