Description Madbull Complete Tracer Hop Up Unit For M4/M16 Ultimate 3-in-1 Hop Up Chamber Unit with Tracer LED Module for M4 / M16 Series MADBULL Madbull describe these as the ‘’Ultimate hop chamber’’ and in my opinion they are correct. Two versions are available, with and without the tracer module (both of which we sell). The hop chamber includes an o-ring seal which reduces pressure loss where it connects with the gear box and a rotary control which we have found to be more stable (less likely to move by its self) than the more normal M4 types. For CQB, Urban or night use the tracer module is quite incredible. Being contained within the gun an external tracer unit is not required, keeping the gun short and externally unchanged. Assembly & fitting required.
