I hope it's OK to resurrect this thread.
I recently purchased two D5 pumps from Primochill to use with the Eisdecke dual PMMA pump top (13312).
I purchased the Eisdecke from Performance PCs in Florida, online.
The D5 pumps are custom-labelled Laing D5 units (it says Laing D5 Pump right on the label).
Primochill does not ship o-rings with their pumps, and Alphacool does not ship o-rings with their pump tops.
So I need two o-rings (+ spares preferably), and am trying to find the correct size.
Several vendors sell "D5" o-rings but they are all listed as different sizes.
I've seen 57 x 3.5, 60 x 3, even 61.8 x 3.5!
The extended part of the pump case that enters the Eisdecke measures 61.5mm OD, and the bore into which it seats measures 65.5mm ID.
However there is what looks like an o-ring groove at the bottom of that bore that measures 2.9mm deep, with 53.4mm ID and 61.6mm OD. So the width of this groove is 4.1mm, which along with its depth of 2.9mm seems clear that this groove is where the o-ring should go. Based on the groove dimensions it would appear your 57 x 3.5mm o-ring must be dimensioned such that 57mm is the AVERAGE of the o-ring's ID and OD. Whereas the other rings I see listed various places are perhaps giving the OD of the ring. Does this make sense?
I'm ready to buy some of your rings, or others dimensioned as 57 x 3.5mm, from Performance PCs, but want to make sure I'm getting the correct size.