Stem Count On Dual Lock

For nearly everyone, you want to use 250 to 250.  Originally Dual Lock was 170 to 400.  250 count was later developed to make Dual Lock more convenient, so that there is no need to have 2 parts like in hook and loop fasteners. 

To identify use the last number in a part number
ending in 0= 250stems/inch
ending in 1= 400stems/inch
ending in 2= 170stems/inch

for example: SJ3540, SJ3541, and SJ3542

Here is a handy little chart to for the different combinations of dual lock counts:

170 to 250	Easy opening for multiple closures.  Low engagement force, low tensile strength.
250 to 250 or 170 to 400	Most Common:Medium engagement force balanced with moderate tensile strength.
250 to 400	Higher engagement force balances with high tensile strength.
Dual Lock to Loop fastener	Quick grab engagement, high peel force,very short cycle life