This is a special inner barrel for pdi.jp
Basically PDI has no lined up about 6.08mm inner barrel for GBB.
It's a revival !
Inner Barrel date.
In Dia. : 6.08mm
Out Dia. : 8.55mm
Material : SUS304(stainless steel)
Inner Dia. tolerance : 0.002mm
Length : 138mm
This shape is available to TM GBB HI-CAPA5.1 but the length is customized so stick out for TM HI-CAPA5.1 original slide.
This item has no plastic bag & no label.
It's put in a black plastic tube.