Adapter rings are the link between the lens and the matte box. Each lens will needs its own specific adapter ring.
Flexible adapter ring kit, 143 mm, for MB-4xx matte boxes.
0420-0601
Separate rubber donut set for Flexible donut adapter ring MB-435 and MB-...
0420-0601-01
Separate rubber donut set for flexible donut adapter ring MB-215, MB-216...
0250-0195-01