Bianchi specifically designed the 55L for the small framed hammerless revolvers that are so popular for concealed carry. Security is provided by a retention strap that crosses behind the trigger guard. The release tab is activated by the middle finger during the draw stroke. 1.75” belt loop.

Features:

Fits revolvers with hammer shrouds
Designed for use with rubber hammer shroud grips
Fingersnap strap allows the middle finger to open snap
Rides high and close to the body for maximum comfort and concealability
Suede lined
Closed muzzle
1.75" (45mm) belt slot  

Fits:
Smith and Wesson Model 640-1 and similar sized .357 Magnum "J" Frames