A tanzen obi is a small, lightweight belt used to tie together a tanzen (thick, padded jacket), haori (kimono jacket), and a kimono.
These are also oftentimes used in places like an onsen (public bath) or ryokan (Japanese-style inn), typically with a yukata. These should not be worn formally and should only be used indoors. A heko obi or, better yet, a kaku obi should be worn by men when outdoors.
Due to their size and oftentimes being fairly malleable, tanzen obis are sometimes used as a datejime (a strap underneath an obi to hold up the kimono).

Blue/Red/White:
Synthetic, Very stiff
A - Few signs of age & use may be seen.
Width: 5.5cm (2")
Length: 242cm (95")

Brown/White:
Appears to be polyester
A - Few signs of age & use may be seen.
Width: 6.5cm (25.5")
Length: 219cm (86")

Age:
Before 2002

Cleaning:
Dry Clean Only!
Air outside on a dry day a couple times a year.