The Eagles are apparently using a 1m long bat weighing 1,000 grams in order to teach players how to use their bodies (and make use of centrifugal forces) more efficiently. The Eagles only have one of these bats at camp right now, but will be getting in 30 before spring camp.
Incidentally, head / batting coach Koichi Tabuchi apparently suggested the bat. Seems he used it back during his Seibu days.
Seems Rakuten Eagles' head / batting coach Tabuchi wants to see Masahiro Tanaka get a nickname that ends with "chan" since Tabuchi's own nickname was Butchan.