Glass seed beads come in many sizes and from many countries. I have used Czech seed beads and Japanese Miyuki seed beads in many of my projects and like both kinds. I have used as small as 15/0 and as large as 6/0.

              There are some differences to the two kinds I have used. Miyuki Seed beads are more uniform in size and shape and the holes are more even than the Czech Seed beads. The colors available from Czech seed beads are good but Miyuki has some additional color variations that are not available from Czech seed beads.  Miyuki seed beads are more costly than Czech seed beads .

        Crafts-by-Kathie's Ebay Store      

11/0 seed beads

• 11/0 seed beads are 2.1mm in size
• 2.2 mm in size for Japanese Seed beads
• 4,000 pcs per hank 
• About 17 beads per inch.
• About 40 grams per Hank (Czech only)
• My Miyuki seed beads are sold by 2 1/2" tube containing 10 to 12 grams
• each tube of 11/0 seed beads contain approximately 950 seed beads
• 11/0 seed beads ebay store Link

8/0 seed beads

• All Glass size 8 seed beads
• Made in the Japan by Miyuki
•  or Made in Czech Republic
• I sell all 8/0 seed beads by 5 inch tubes 
• 8/0 are About 3.1 mm in size
• a 2 1/2" tube contains approximately 10-12 grams of seed beads
• each tube hold approximately 375 size 8/0 seed beads
• These make excellent spacer Beads.
• 8/0 seed beads    Ebay store Link

6/0 Seed Beads

• All Glass size 6 seed beads
• Made in the Japan by Miyuki
• or Czech Republic 
• I sell all 6/0 seed beads by 2 1/2 inch tubes 
• 6/0 are About 4 mm in size
• a 2 1/2 inch tube contains approximately 10-12 grams of seed beads
• each tube contains approximately 125 size 6/0 seed beads
• These make excellent spacer Beads.
• 6/0 seed beads       Ebay Store Link