Is it a reciprocating saw shape or the type with the "vertical" motor? Got a pic. ? Got any other systainers to test fit it in?
If it the Recip shape it might not fit at all.
My Bosch (vert motor style) fits in a Sys -II , I added a lift out tray for the bits. Plug in so no battery or charger, not much extra space so I think you will need a III or maybe a IV.
Seth