The RockSEAL® II packer is a dual-element open hole packer that provides high-performance zone isolation, ensuring stimulation of the targeted zone and isolation of water/gas shut-off to optimize long-term production. The hydraulically set packer combines the sealing strength of a mechanical element with the setting force of a dual-piston cylinder and mechanical body-lock system. The packer has a specially designed elastomer with the largest possible cross-section to provide excellent expansion ratios to set in oversized holes. The packer is also designed with anti-preset features that allow it to be pushed through tight spots in the well without pre-setting or shearing the packer.