Originally posted by Not a Number I bought those from the same seller in 2012. There are very minor differences between those and the OEM Pentax caps - the textured areas are different, the mold release marks aren't the same and the lettering is quite as "sharp". Most likely casts and molds were made from the originals. The counterfeit caps are much more snug - I can't remove them easily single handed (which is what you wanted).
They do the job and are practically indistinguishable from the "real" thing. A great value for the money.
I have also ordered that 10x set from same Rainbow... seller few times (maybe 6 times) in last years. Lasttime was few weeks ago, few caps used from that set and they were just fine. But I remember getting set also that most caps were too tight, maybe it was second set I did order. But in general those caps are ok and very difficult to tell if original or not. Maybe few last sets been have little grayish black color...