Aaron is 100% right, these BP starters should not be used in Composite motors. For small composite motors, Quest igniters work quite well. For anything above 29mm, I find it preferable to make my own.
Having said that, you can use these BP igniters if you dip them in ProCast (from Quickburst -
http://quickburst.net/qb/procast-order-page/).
If you dip the BP starters in ProCast -
make sure it still fits in the core of the motor! Unlike BP motors, most composite motors are NOT end burners, the starter needs to be inserted all the way to the top end of the motor grains. Especially on 18mm and 24mm composite motors, the core diameter is very small. In some motors, such as the Aerotech E20, that use a C-Slot, it would be almost impossible to insert a dipped e-match. As a test, hold the starter on the outside of the motor with the end near the end of the motor case where the grains would likely end and mark the length on the starter. That will give you a rough idea of how far you will need to insert the starter.