SPR stands for Spacer Pad Response. It is a bearing and response system produced by Buzz-On, intended to allow easy modification of yo-yos. The SPR is, essentially, oversized bearing spacers. The bearing is held between the two spacers by a small bearing seat. The rest of large brass spacer is smooth and flat, allowing a yo-yoer to place any of a variety of friction stickers on it. While SPR kits were originally produced specifically for Buzz-On products, they found widespread use in other brands' yo-yos for quick and inexpensive bearing and response pad modification.