I have grown Kotlas many years. It is almost identical to Stupice. It matures a day or two ahead or behind Stupice. The tomatoes are the same size. I have never seen a determinate Kotlas. All mine were PL and grew about 4 feet tall so small for an INDET. Seeds from Johnny's. Seeds originally called Sprint. NOT from Russia. Named Kotlas by Johnny's to honor their sister city in Siberia. I've kept the seeds pure all these years. Grew a plant in my dining room window this past winter to update my Kotlas seed collection and to enjoy homegrown tomatoes throughout the winter.