I ordered 3 glass cap's with the honeycomb air intake's i have not had any problems with them. The replacement glass fitted better than the one that came with it
First the o rings tolerance is way too high. The glass cap will go on after some VG applied but it's really really hard to get off. The standard metal will not go on at all with the o rings supplied. If you use the o rings that come with the Mongrel the glass cap will not fit on tight enough to hold.
The glass cap broke after refitting. The quality of the glass is not as good as the of glass that comes with the Mongrel.