Ronald Acuña Jr. has a few different bats in the rotation for 2021. Primarily, the NL MVP candidate is swinging the Louisville Slugger A181 (maple), a model crafted for him. Not much information is known about the A181 just yet, but the bats we have seen Acuña Jr. swing have a standard-looking handle and extra-long barrel with no cup. The barrel tapers quickly, meaning that it reaches its full diameter closer to the handle than most bats, making for an end-loaded feel.
Acuña Jr. also still swings the Louisville Slugger C416 (maple) and his personal RA13 (maple) from time to time. The C416 was made for Johan Camargo in March 2019. Just like the A181, the C416 is not available for purchase at the time of this writing. However, you can buy the Louisville Slugger MLB Prime Signature Series RA13 at Baseball Express and Louisville Slugger for $149.95. The RA13 is slightly end-loaded and features a flared knob, AJ10 handle, and I13 barrel.