JEGS Exhaust Manifold Spreader is adjustable, made of high-quality steel, and zinc plated to ensure durability after repeated use. Made to accurately align bolt holes on your cylinder heads and prevent cross-threading by simply expanding a warped manifold. Place the spreader between the manifold flanges and adjust the spreader length using a 3/4” or 19 mm open end wrench. When the spreader has aligned the bolt holes, bolt down your manifold. Works best when used in pairs. Designed for use on GM small block V8 engines, but can be used on many applications that just need the slightest spreading.