The dual-plane technique is graded I, II or III according to how much the muscle is released from the breast tissue along the lower border, which changes how much the breast tissue can redrape over the implant.
Dual Plane I
This is the most conservative version, with minimal release of the muscle along the lower edge. The muscle–gland relationship stays largely intact.
Who it suits
Dual Plane I is generally chosen for breasts with most tissue sitting above the inframammary fold, minimal sagging and a tight lower pole — for example many first-time augmentations in younger patients with firm tissue.
See also Dual Plane II, Dual Plane III and muscle release explained.