"" (ブースターパック Būsutāpakku, "Booster Pack") are packs of cards that are used to build or edit decks. Each pack contains 5 of over 105 different cards, while a display box contains 30 packs. Unlike Trial Decks, the cards contained in boosters are random and from several different Worlds.
The ratio of rarity is divided into BR/RRR/RR/R/U/C, in addition to this, 12 of them are also SP. The Buddy Rare (BR) is a unique card that also will come in the next set.
The ratio of rarity in a display box is 2 RRRs, 6 RRs and 22 Rs. If a SP card appears, it replaces 1 of the RRRs in the Japanese version instead, however it replaces 1 of the RRs in the English version instead. As of BT03, the rarity ratio was changed to 3 RRRs, 5 Rs, and 22 Rs. In a case of 16 boxes, there are 4 SPs and 1 BR.
As of BT03, parallel foil versions of R or lower cards were added. These are randomly distributed in packs, and the ratio in a display box is 1 parallel foil R, 2 parallel foil Us, and 3 parallel foil Cs.
As of April 3, 2015, this series is replaced by the "H (Hundred) Booster Set" series in the Japanese format, and as of May 1 in the English format. Both of them add Secret Packs, a special rare pack that replaces 3 normal packs in a case of 16 boxes. SPs were changed to always have alternate art, but the number per set was reduced to 3 or 4. SPs are also now only 2 per case.
As of April 15, 2016, this series is replaced by the "D Booster Set" series in the English format.