We checked the sizes of the spare set o-rings. Unfortunately our measurement cannot be super accurate since we do not have a caliber. However the difference 50 vs 52 mm / 208 vs 217 mm is obvious. Result: 50 mm o ring is 50 mm; 208 mm o-ring - circumference = 665 mm -> outer diameter = 211.6 mm -> inner diameter = 208.6 mm. (+/- 1 mm). Within the measure accuracy it seems that the o-rings as delivered have the correct size. We are sure we got 4 & 8 identical o-rings. We will order replacement for the o-rings you have in Nashik to be sure this will be no show-stopper. I will bring o-rings during my visit. Nevertheless we have to find the cause for the larger size of the o-rings in Nashik. Can you please check is the o-rings were submerged in oil to facilitate mounting them. EPDM swells in oil (also vegetable) this might be the cause of the larger size.