The above illustration (found here) demonstrates the dimensional differences between phase correction tubes in Ocharaku's latest Sakura Plus and Akazakura Plus earphones.

They are:

1- 2mm difference in length
2- same longitudinal length
3- 1mm difference in height (when resting on its foot)
4- this results in a frequency response shift of 400Hz

Ocharaku suggests that the length of one or the other tube corresponds to the length of the ear canal. The phase correction tube best matching your ear canal will sound more natural.

Relevant links:
ohm image: ohmage to the Ocharaku Flat4-KURO
ohm image: ohmage to the Ocharaku custom-modded Audio ...
touchmyapps: TouchMyApps Review: 音茶楽 Flat4-楓 Ocharaku Flat4-KAEDE ...
headfonia: Ocharaku Flat-4 KAEDE Type II - Tremendous Wood
headfonia: Ocharaku Donguri-Keyaki