Series 150 releasing and circulating overshot consists of three main external parts: a top sub, a bowl, and a guide. Internal catch and pack-off parts are determined by the diameter of the fish. Each Series 150 Overshot assembly is designed for a maximum catch diameter. A Spiral Grapple, Spiral Grapple Control, and a Type A Packer are used in the overshot bowl when the diameter of the fish is near the published maximum catch diameter of the overshot. When the diameter of the fish is considerably below the maximum catch diameter of the overshot (usually 1/2”), a Basket Grapple, a Mill Control Packer, or Basket Grapple Control are used in the overshot bowl.