H & H’s TK-4 tourniquet, in 2007 tests by the U.S. Naval Experimental Diving Unit, demonstrated successful arterial occlusion capabilities with the exception of the application of the tourniquet at the top of the leg. In fact, ALL of the tested tourniquets failed 33% of the time when applied at the top of the leg. This is unacceptable.
When tourniquets are applied at this point on the leg over materials such as a uniform, as is normal, the tourniquets were either not strong enough to fully pressure the area or the users could not or would not place maximum force on the tourniquet.
In order to allow the user to put maximum pressure wit the tourniquet, H & H modified the TK-4 to create the TK-4L to give the user the ability to apply the maximum capable force on lower extremities.
The TK-4L updates the TK-4 design by putting a tension fixture at one end of the strap. The added aluminum tension fixture results in the ability to apply maximum manual force to the strap and increase the blood loss stoppage capability of the strap.