The 2/35mm Biogon ZM T* is small - shockingly small compared to the Distagon ZF.
I decided to get the Zeiss Ikon kit with the 35mm Biogon as my first lens. I have a preference for the 35mm focal length for everyday shooting and this Biogon is, I believe, the best 35mm lens ever made by anyone. The Summicron ASPH is a great lens for sure, but you have to assign high value to its 20~25% smaller size (*) because on paper the Biogon is actually a better performer and costs 3x less.
In your hands the lens is wonderful. It's cute. I wish it had a rectagular hood though.
(*) It's all about viewfinder obstruction.