The Pokémon Shirts polo shirt line, a collaboration between Pokémon and the online custom shirt brand Original Stitch, will be updated in mid-May 2021! New variations will be added to the polo shirt line, the Pokémon embroidery and the buttons that can be selected in the customization options.

To commemorate the renewal of the polo shirts, they are holding the "My Favorite Monster Ball Vote" on Twitter from March 12th, 2021 at 11:00 a.m. JST until to March 19th, 2021 at 11:59 p.m. Participants can vote for your favorite monster ball! The top three monster balls will be added to the button designs on the polo shirts.

How to vote

All you have to do is tweet on Twitter the two following hashtags "#Ball Support Vote" (#推しボール総選挙) and "#Vote for ○○" to complete your vote. In "#Vote for ○○", put the name of your favorite Monster Ball in place of the "○○". For example, if you want to vote for Master Ball, tweet #推しボール総選挙 and #マスターボールに投票.

For more information on the types of monster balls you can vote for, check out the list at the bottom of the page. The results will be announced later on the official Pokémon Shirts website. If you edit or delete the designated hashtags, your vote may not be accepted. Please do not edit or delete the designated hashtags if you wish your vote to be counted.

Monster balls that can be voted for:

・Master Ball (マスターボール)
・Premier Ball (プレミアボール)
・Heal Ball (ヒールボール)
・Net Ball (ネットボール)
・Dark Ball (ダークボール)
・Nest Ball (ネストボール)
・Quick Ball (クイックボール)
・Timer Ball (タイマーボール)
・Repeat Ball (リピートボール)
・Dive Ball (ダイブボール)
・Gorgeous Ball (ゴージャスボール)
・Safari ball (サファリボール)
・Precious Ball (プレシャスボール)
・Ultra Ball (ウルトラボール)
・Lure Ball (ルアーボール)
・Level Ball (レベルボール)
・Moon Ball (ムーンボール)
・Heavy Ball (ヘビーボール)
・Speed Ball (スピードボール)
・Friend Ball (フレンドボール)
・Love Ball (ラブラブボール)

Source: https://www.pokemon.co.jp/info/2021/03/210312_cm02.html