What is claimed is the ornamental design for a holster, as shown and described.
FIG. 1 is a perspective view of the invention without a cover;
FIG. 2 is a front view thereof;
FIG. 3 is a back view thereof;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is right side view thereof;
FIG. 7 is a left side perspective view thereof;
FIG. 8 is a perspective view of the invention as shown in FIG. 1 with a firearm engaged therein;
FIG. 9 is a front view of the invention being worn about a chest of a user and having a firearm engaged therein and further having a cover attached thereto, but not engaged thereover; and,
FIG. 10 is a front view of the invention being worn about a thigh of a user and having a firearm engaged therein and further having a cover attached thereto, but not engaged thereover.
The broken line showing of portions of the holster is included for the purpose of illustrating environmental structure and forms no part of the claimed design.