It seems there is a general consent among the martial arts population (Kendo, Aikido, etc.) when selecting Keikogi or Hakama for purchase, the product description will often indicate a number such as #5000, #8800, or #10,000 that is often confusing. People generally end up making their selection based on price instead of knowing exactly what they have selected. To demystify this number, we will try to look at these numbers from a slightly more scientific approach. 

These numbers are actually a represenatation of the size and number of threads per square inch.

Lets get some definitions out of the way:

• Thread (Th.) - a single piece of fiber
• strands (Str) - one or more threads twisted together
• Gauge - thickness of the thread (the larger the number, the finer the thread)
• Vertical Measure - vertical length of the Hakama cloth
• Horizontal Measure - Horizontal length of the Hakama cloth

Meaning:

• #5000 Fabric Keikogi / Hakama uses single thread weaving with 16 gauge fabric thickness and has 60 x 74 strands of threads per square inch.
• #8000 Fabric uses double thread weaving with 30 gauge (finer) fabric thickness and has 60 x 52 strands of threads per square inch. 
• #10000 Fabric uses double thread weaving with 30 gauge (finer) fabric thickness and has 63 x 54 strands of threads per square inch. 

Summary:

• The #8800 Hakama and #11000 Hakama has the best overall shape and is made with finer fabric that will protect better.
• #5000 Hakama is softer but thiner.