This graded dilator set is designed for UBE and DELTA large-channel minimally invasive spine surgery. Multiple diameter sizes enable step-by-step dilation from thin to thick to gently expand muscle and fascia, minimizing soft tissue laceration and intraoperative bleeding. Clear depth markings on the shaft allow precise insertion depth control. The mirror-polished smooth surface creates low friction when passing through tissues. Fabricated from rigid medical stainless steel that resists bending and corrosion, the instruments tolerate repeated autoclave sterilization for cyclic use in all kinds of spinal endoscopic decompression procedures.