Unlike the previous forms, Gear 4 focuses on compression more than stretching in a manner similar to the Bane Bane no Mi. While Luffy is using Gear 4, his physical strength and speed are increased to the point where he is able to overwhelm a Warlord of the Sea, Donquixote Doflamingo, and the second strongest member of an Emperor's crew, Charlotte Katakuri, whereas before, Gear 2's lack of strength and Gear 3's lack of speed made them ineffective in the fight. Depending on the situation, Luffy can adapt Gear 4 into different forms.

Combined with Luffy's rubbery composition and his compressed muscle structure, Gear 4 both adds explosive power to Luffy's attacks and grants him enhanced defensive capabilities far beyond what he can demonstrate with or without Gear 2 or Gear 3. Similar to when using Gear 2, Luffy is continuously emitting steam in this form. He also physically grows taller, standing around 4 meters tall. The Haki coating across his body resembles the wispy ends made from flames, giving it the appearance of tattoos, and he gains shading around the inner and outer edges of his eyes. When utilizing Gear 4, Luffy makes extensive usage of his Busoshoku Haki by coating his arms, legs and much of his torso in it to the point that they turn black from hardening. If Luffy is stopped mid-blowing, the arm will slowly deflate. Similar to how he activates Gear 3, he blows an incredible amount of air into his body, but this time he inflates his muscular structure before distributing the air throughout his body, with emphasis on his upper half. Luffy coats his arm in Busoshoku Haki before biting into his forearm.

Air force 1 snake