This is a replacement Traxxas Short Heavy-Duty Half-Shaft Set, and is intended for use with the Traxxas E-Maxx, T-Maxx 2.5 and S-Maxx trucks. These shafts are installed on either side of the transmission. This package includes two short heavy-duty external-splined half-shafts, two short heavy-duty internal-splined half-shafts and four metal U-joints. NOTE: Will not fit original T-Maxx with .15 engine.