1. Button Material: This is the key distinction represented by "BPM" versus "MPM" in the part number. A22NL-MPM-: The "M" denotes a Metal pushbutton. A22NL-BPM-: The "B" denotes a Plastic (or non-metallic) pushbutton. This difference primarily affects the product's physical characteristics and suitability for specific environments. Metal buttons offer higher mechanical strength, better wear resistance, and a distinct tactile feel, making them suitable for demanding industrial applications requiring high durability or where mechanical impact is a concern. Plastic buttons are lighter in weight and are often the preferred choice in environments with potential chemical exposure or where electrical isolation is necessary; they also typically come at a slightly lower cost (consistent with the observed price variance). There is no impact on pure electrical functionality or mounting dimensions. In summary, the substitution is technically feasible. The final selection depends on the specific requirement for button material (metal vs. plastic) or cost considerations.