Hello friends, the pedals are maked L and R for left and right sides of the bike-as viewed from the riding position. Each pedal is threaded opposite of the other, great care should be used at this point of assembly, and a little grease on the pedal threads is reccomended.
You will never have a problem if done correctly.
I recently bought a 6ku fixie I followed the instructional video and on the first ride my pedals flew right off almost causing me to crash.
My bike just came less than a week ago and I decided to assemble it on 12/7/18. It has only been 4 days of use (not constant) and the left pedal flew off mid- ride which almost led me to get run over. I got back home only to see the inside threading of the crank arm was completely shaved off. I do not hate this bike but if I am paying 200$ and this is what is happening then I think I have to bring this to your attention for the safety of future costumers.
Recently bought myself a fixie from 6ku, within a week of use, one of the pedals came right off as I was using it, I checked to see the problem only to see the threading on the inside of the crankset to be completely flushed out and now I need to pay again to get a new one
careful not to strip the cranks when putting in pedals, especially if your pedals are steel. This crankset is aluminum so steel can over power it carefully. Just a warning. Make sure to screw your pedals in nice and straight