Safariland has a history of making great innovative holsters. The Model 6004 was the beginning of popular kydex type tactical holsters. It was seen on the legs of Green Berets in Afghanistan and contractors around the world
The 6004’s Self Locking System (SLS) used a “bail” or thumb released top strap which retained the pistol but quickly rotated forward to draw. There were two problems. It sometimes hung up on a fast draw and the bail had to be manipulated again to lock the pistol in when holstering.
The ALS® system is the next evolution in retention holsters and builds upon the successful SELF LOCKING SYSTEM (SLS). With many patents to its credit, the key to this system is an internal locking device that secures the weapon in all directions simply upon re-holstering.
The system is modular. For duty use, you can add retention components to elevate retention to Level IV Retention™ with the addition of the Sentry. It is custom molded so it is critical that you get exactly the right model. Holsters with this all-new ergonomic design are completely operable with the thumb making training easy, and the straight up draw makes them very instinctive to use, yet difficult for an assailant’s attempted takeaway.
Once the retention devices are released, the weapon can be drawn straight out of the holster with no twisting or other motion required. Unlike other designs, the unlocking motion of the thumb is a natural part of the draw stroke. I have used this in the field and in 3 gun competition. I say without hesitation, it is the fastest retention holster in the world.
My favorite is the Model 6395 ALS® Low-Ride Level I Retention™ Duty Holster.  The ALS Level 1 retention and hood guard make it secure. The open-top design makes it quick.
The Safari Laminate thermal-molded construction is tough and it protects handgun and sights. The 6395 has a mounting plate which attaches the holster to a duty belt. There is a low ride and a mid ride version. This solves the problem of the leg strap, there isn’t a leg strap.
The holster is low enough for good ergonomics and it ride below your armor. It is stiff enough to provide a good base without compromising your flexibility. Depending on your gun/light combination and options, these babies go from $105.00 to $177.75 from these guys
http://www.holsters.com/duty/holsters/model6365.asp
Level III Retention, ALS (Automatic Locking System) secures weapon once holstered, also features the SLS (Self Locking System) Rotating Hood
Low-Ride level
Low-Ride, this slim, compact design allows weapon to ride close to the body
Simple straight up draw once all releases are deactivated
2.25″ (58mm) belt slots
ALS Automatic Locking System secures weapon once holstered; simple straight up draw once all releases are de-activated
Slim, compact design allows weapon to ride close to body
