Gas blocks are crucial components in the AR-15 gas system, serving as the intermediary between the barrel and the gas tube. Positioned over a small gas port drilled into the barrel near the muzzle, the gas block's role is to capture a portion of the high-pressure gas produced during firing and redirect it into the gas tube. This redirected gas then travels back to the bolt carrier group, enabling the firearm's semi-automatic cycling. Gas blocks come in various designs, including fixed and adjustable versions. Fixed gas blocks deliver a consistent amount of gas, while adjustable gas blocks allow the shooter to fine-tune gas flow, optimizing rifle performance for different ammunition types or suppressor use. They are typically secured to the barrel via set screws, clamps, or a taper pin system. Gas blocks also come in different profiles, such as low-profile or railed, to accommodate different handguard styles and accessory needs. Ultimately, they ensure the reliable cycling of the AR platform, making them indispensable to the gas system.