Concentrated is the one skin available in the Birthday Time offer. It could be acquired as part of a limited time item deal in mid July 2020.
Concentrated could only be acquired after purchasing both Deal 1 (22000 coins) and Deal 2 (2200 DNA) for $9.99 each. Then, the skin, two 3x XP Boosts (24 Hour) and two 3x Mass Boosts (24 Hour) would be unlocked. Concentrated was not available for individual purchase and may not be available for purchase in the future.
Details of this skin may vary depending on location, platform or time.