These are sold in packages of 5, 10 or 20.  Measurements are listed below. Most are used for 1/8" rope, cording, bungee etc.. some are for smaller, and some are for bigger. Please see the measurements below. Made in USA and Taiwan 

Inches -- to MM----1/8 inch is close to 3mm, 1/4 inch is close to 6mm, 1/2 inch is close to 12 1/2mm, 1 inch is close to 25mm, 1-1/4 inches is close to 31mm, and  1-1/2 inches is close to 38mm. Hopefull that helps.

#2 -- BLACK - FLAT -- CENTER HOLE=8mm. WIDE=20.90mm, TALL=26.74mm 

#4 -- BLACK - BUTTON / DRUM, DOUBLE HOLE— CENTER HOLE=5.95mm. WIDE 19.30=mm, TALL=15.30mm

#5 -- BLACK - BARREL CYLINDER -- CENTER HOLE = 7mm, WIDE = 13.75 TALL = 31.10

#7 -- BLACK-- BEAN DOUBLE HOLE/ PUMKIN — CENTER HOLE=5.20mm. WIDE=24mm, TALL=21mm

#8 -- ANTIQUE BRASS-PLASTIC -- ROUND BALL -- CENTER HOLE =6.mm. WIDE=18mm, TALL=22mm

#9 -- BLACK -  MINI OVAL-- CENTER HOLE= 5.4mm. WIDE=10.5mm, TALL=21mm

#10 -- BLACK - OVAL— CENTER HOLE=6.50mm. WIDE=15mm, TALL=26.50mm

#11 - BLACK - MINI ROUND BALL--CENTER HOLE=5.40mm. WIDE=15.50mm, TALL=18mm

#12 -- BLACK- ROUND BALL-- CENTER HOLE =6.50mm. WIDE=17.58mm, TALL=21.50mm

#19 -- RED- CYLINDER --CENTER HOLE=5mm. WIDE=12mm, TALL=25mm

#20 -- BLUE-CYLINDER --CENTER HOLE=5mm. WIDE=12mm, TALL=25mm

#24 -- BLACK- MINI- OVAL -- CENTER HOLE=6.5mm WIDE=12.5mm, TALL=21.11mm

Thanks for looking have a great day!