In order to specify the apertures needed for Recycler Collimators and Masks, we will explore the vertical aperture requirements implied by the nominal vertical beam pipe size and examine the lattice functions to find the largest vertical beta. For horizontal aperture requirements we will assume full vertical to horizontal coupling and add to this a requirement for the momentum spread and slip stacking offsets. To these requirements an allowance for injection errors will be added to arrive at an aperture requirement. Using a nominal beam emittance of 15 pi-mm-mr and the same momentum spread and slip stacking momentum requirements, we will determine the nominal beam size. The amplitudes required to move this beam edge to the aperture edge will set the maximum bumps needed for collimation. Since collimators will define apertures inside of the Recycler aperture, the bump amplitudes for collimation will be smaller than determined here. This is not a specification document but it will describe the basis we will use to define collimation system requirements.