I recently purchased a second hand Swarovski Z8i. Absolutely fantastic scope and to my eye is crystal clear. However 2 friends of mine who are a good bit older have looked through it and said there is a small spec inside the reticle. They both described it the same but one said he could see it slightly lower down than the other person. Anyway no matter how hard I look for it I can’t see it. I would say my eyesight is spot on. I asked my wife to look though and she couldn’t see it either. Can anyone explain this? Cheers