This is a Uncle Mike's Inside Waistband Holster known as the IWB Tuckable Holster, model 55190.
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:
Ambidextrous
Ideal for Concealed Carry
Passive Retention