This adapter allows using one of Krasnogorks-2 lenses (50mm Vega-9) on non-reflex cameras with Arri PL mount. Let me explain both points:
1. Krasnogorsk-2 has three prime lenses - 12mm, 20mm and 50mm. 12mm and 20mm DON'T fit this adapter since their focusing rings are too close to the flange. They just can't reach infinity on PL mount due to this housing feature.
2. 50mm lens fits the adapter perfectly, but doesn't clear a mirror shutter even at closest focus distance. Therefore, you can use it on non-reflex cameras only.
Yet another Krasnogorsk-2 lens is Meteor 5-1 zoom. But it has both problems at once - doesn't fit the adapter full way, and doesn't clear the shutter.
Mentioned limitations aren't related to the adapter. The problem is with lenses.
Используйте пробелы для отделения меток. Используйте одинарные кавычки (') для фраз.