With the shallow head on the stock bolt, it is common for the head to round out during removal. The MA Heavy Duty Injector Return Line Bolthas been redesigned to allow nearly double the tool engagement.
Proper engagement of the Allen wrench is crucial for accurate torque during reassembly to avoid a fuel leak at the return line fitting. The unique head shape offers the needed strength while maintaining proper clearance on other engine components.
It's common for these to round the head when removing them. If the socket does not fit in the bolt properly, it can not be tightened properly and this could lead to a leak, putting fuel in the oil. Replace this bolt if damaged to avoid expensive problems.