Upgrade items are available in different rarities. The rarer the upgrade item, the greater the stat improvement it provides. The number of shards you need to redeem to create an upgrade item increases according to rarity.
Bees with higher stats bring back more Honey, find Honeypots quicker, and have better chances during Raiding and Defending missions. Be strategic in your upgrades to build the best Bees you can!
You can increase your Bee's stats by visiting the Bee Lab.