The inner diameter is 7.0mm (1/4") before shrinking.
After maximum shrinking the inner diameter is 1.75mm (1/16").
Shrink ratio of 4 to 1.
1 meter of heatshrink makes 66 15mm pieces. This is enough heatshrink for one 24 pin cable and one 8 pin cable plus a little extra for mistakes. Alternatively it is enough for two PCI-e cable sets (8+8 or 8+6) plus a little extra for mistakes.