Master Yi Runes explained
There's one set of runes for Master Yi on patch 14.21 that is the clear favorite for LoL players and pros alike. The best Master Yi rune paths on the position 
Jungle are 
Precision as the primary path and 
Inspiration as the secondary path with a pick rate of 50%. Besides picking runes on Master Yi you should learn how to play Master Yi and if you are interested in pro matches take a look on how a pro builds Master Yi. If you want to discuss 
Master Yi then you should visit the champion subreddit.
Master Yi runes from primary path
Precision improves attack and sustained damage on Master Yi troughout the match. Most of high elo players – and our LoL pros in the the major regions – have agreed that 
Lethal Tempo is the best keystone rune to run on Master Yi. This keystone rune gives Master Yi a great head start in team fights and allows to put out more damage in that time window. Other primary runes on Master Yi are 
Triumph, 
Legend: Alacrity and 
Coup de Grace.
Triumph restores on Master Yi a part of missing health and award bonus gold, if a champion is killed. Legend: Alacrity grants additional attack speed to Master Yi. Master Yi deals with Coup de Grace more damage to targets with low health.
Master Yi runes from secondary path
When it comes to your secondary path, most Master Yi players prefer to go with Inspiration. Inspiration opens creative opportunities on Master Yi troughout the match. On the Inspiration path, the best runes for MasterYi are Magical Footwear and Cosmic Insight.
Magical Footwear allows Master Yi to focus on those essential core items without the need to spend the additional 300 gold on boots. Cosmic Insight grants summoner spell and item haste.
FAQ for Master Yi Runes
Which is the best keystone rune on Master Yi?
The best keystone rune on Master Yi is Lethal Tempo. This Master Yi runes setup is then referred as Master Yi Lethal Tempo.
What runes does Master Yi use?
Runes from the paths Precision and Inspiration are the most used runes on Master Yi. For the exact pick rates of Master Yi runes used, you have to study the rune distribution presented.