Hi,
On the last page of the rules, it states the following:
Wooden pieces, 150 mm x 50 mm x 30 mm, painted in the team colors on 2 of these larger opposite sides, the other side stay clean, with a vinyl on which are the tags aruco 36 and 47. Their weight is not defined and depends on the organisation.
From what I understand, since organizations are not forced to use the official Jenga set and are allowed to make the pieces on their own, a weight cannot be given accurately
We made our pieces using a similar wood to the Jenga set, and they weigh about 110 grams each, so I would estimate a range of 100-150 grams per piece, however, that is still a guess.