40mm for the K01
Losing the rubber lens cap for the XS 40 was my biggest concern when the K 01 first arrived. I now am just extra careful with it. I actually hold it in my left hand or throw it back in my small bag as I shoot.
I have just gotten myself in the habit that I am either going to hold it or put a lens cap back in the bag. After the XS 40, I do not even put lens caps in my pocket anymore. After a few thousand photos, I still have the original lens cap.
The other thing is to get in the habit of pushing all the way around the perimeter when putting it back on. If not, it may fall off. I have had this happen with the old plastic cap type used on the ol 50/2 and 28/2.8. They will fall off on their own so they got replaced before being lost.
Variance is Evil!