First mentioned in late August when MG Astray Blue Frame Second Revise was announced, this special prize will be included for the mentioned MG kit, which will allow you to assemble backpack connector parts for various backpack units from MG and 1/100 SEED/Destiny kits to be used on each others. All four types as shown.
The emphasis however, is the compatibility between SEED VS Astray units.
Just a single runner actually ^^;
It's explicitly stated that this item is NOT for sale. So you know what's going on if you see shops put this up for a different price when MG Astray Blue Frame Second Revise is out (October 22nd, 5,040 Yen inclusive of tax). X_X
Image is from Bandai Asia Web.