This is a Uncle Mike's Holster known as the Inside Pant, model 8912-2.
These inside the waistband holsters are ultra thin four layer laminate that are no thicker than conventional suede leather holsters. The internal moister barrier won't transmit perspiration to the gun and the smooth nylon lining make for an easy draw. This is the open top style.
Features:
Size 12
Left hand
Fits Glock 26, 27, 33 & other sub-compact 9 mm/.40 cal