Bead Sizes
 
Bead sizes are traditionally given in mm (millimeters.) As a penny is 19 mm across, the penny in this photo should give some idea of the size of beads used most often in necklaces. Or see below where 2, 4, 6, 8, 10 and 12 mm are compared to a one inch measurement.
 

 
As there are 25.4 mm in one inch:
It would take
approximately 12 2mm beads to equal one inch,
approximately 6  4mm beads to equal one inch,
approximately 3  8mm beads to equal one inch,
approximately 2  12mm beads equal one inch.
 
A 6mm bead is about 3/16" or the size of the average pencil eraser
and a 10mm bead is just over 3/8 inch in diameter
We use 8mm beads in most of our necklaces. Click on the
Selection page to see how they look when strung.

 

enlarged

 
Lobster clasp
 
The lobster clasp is a secure clasp in that it cannot be opened accidentally. Reminiscent of a lobster's claw, the spring-loaded claw closes securely when the spring is released.

General terms indicating necklace lengths:
 
"Collar" length necklaces are 12-13 inches long and fit around the middle of the neck.  
"Choker" length necklaces are 14-16 inches long and fit around the base of the neck.  
"Princess" length necklaces are 17-19 inches long and lie just below the throat.  
"Matinee" length necklaces are 20-24 inches long.  
"Opera" length necklaces are 28-34 inches long.  
"Rope" length necklaces are 45 inches and longer.