The Gotoh SG381 is a style of machine head (a.k.a. tuning peg) installed on a number of Ibanez guitar models. It is manufactured by the G-GOTOH Gut Co., Ltd. in Japan. The Gotoh SG38 is a predecessor model which is virtually indistinguishable.
The SG381 offers a 1:16 gear ratio. Versions are available for both inline and 3-on-a-side (L3+R3) headstock configurations. A variety of button shapes are also available, though most Ibanez guitars are equipped with style "07" which is an ovaloid shape with squared off sides (as shown in the black peg in the image above). It is available in locking and non-locking versions.
MG-T locking mechanism
The Gotoh MG-T (Magnum Lock-Trad) mechanism allows the user to lock the tuners once the instrument is in tune. It features a thumbscrew locking mechanism to stabilize tuning while playing and preventing incidental contact with the tuners from altering the instrument's tuning.
Height adjustable locking posts (H.A.P-M)
The SG381 is available with height-adjustable posts (H.A.P). This allows the user to adjust individual strings to dial in the oscillation, which contributes to sustain. The H.A.P-M design combines the adjustable post height with the Magnum Lock system.