Ingersoll Rand PETStar® 4 reciprocating air compressors offer durability and reliability combined with four-stage energy savings. Standard PET reciprocating compressors feature three-stage compression. Ingersoll Rand maximizes efficiency with four stages of compression, which significantly increases efficiency over three-stage designs. Combined with industrial grade components and double-acting cast iron cylinders, PETStar® 4 compressors provide supreme durability that reduces maintenance requirements and lowers lifecycle costs.