This is by far one of my favorite things to do, especially when I am making 37mm firework type rounds.  

Both the 37mm star cluster kits and 37mm firework kits can be used together to make some really fun projectiles.  One of my favorite effects for these 37mm rounds is to line the outside of the plastic projectiles with the flying fish bee fuse included in our 37mm firework kits, and then place a small pile of the star cluster stars in the middle.  Cap the projectile with the included paper disc and fill the rest with hot glue.  Finally while the glue is hot place the cap on the end of the projectile and it is ready to load.  This 37mm round will give you a cool combination of brilliant stars and that awesome colored fuse that zips around in the sky.  

Additional 37mm projectile combinations include star cluster stars and thermite poured around the stars.  This 37mm projectile yields a cool brilliant star effect with bright molten yellow sparks that shoot in all directions.  That one is always a crowd pleaser.  Feel free to add any other 37mm combinations you feel comfortable talking about in the comments section.