The Golden Gauntlet is a special weight that Shiraishi wore on his left forearm, hidden by the bandages.
Two years ago, his coach, Osamu Watanabe, gave Shiraishi a golden gauntlet for him to wear on his left arm and "instructed" (in other words, lightly suggested) Shiraishi to wear it until his graduation. To avoid attention, Shiraishi hid the golden gauntlet with bandages (and gave Kintaro the impression that under his bandages contained lethal poison). Since gold is 3 times heavier than lead and iron, and since Shiraishi can play normally even with the golden gauntlet on, when he takes the gauntlet off, his swing speed skyrockets compared to his normal strokes. However, only the speed of his arm increases.