The Holley LS1/2/6 Ultra Lo-Ram intake manifold kits are designed for GM LS Gen III and IV engines equipped with GM LS1/2/6 (cathedral port) cylinder heads. These intake manifolds will work with OE or aftermarket cylinder heads. Plenum top is machined for a standard "large" 6-1/8 in. x 3-1/8 in. burst panel. SFI approved burst panels, burst panel frame sets, and gaskets may be purchased from various manufacturers such as Allstar Performance or Specialty Fasteners The Ultra Lo-Ram intake manifolds are designed for forced induction (supercharged or turbocharged) engine applications and the 105 mm throttle body part number 112-581 or similar models. The base intake manifold is designed with a lower overall height to fit under a stock or mildly modified hood. The 300-623 Ultra Lo-Ram front-feed plenum entry was configured to provide a very low profile modular intake manifold suitable for turbocharged or centrifugally supercharged engines. The fuel rail kits come with two sets of brackets. A set for long (usually standard length) fuel injectors and a set for short (such as Pico, or LS7) fuel injectors.