I love sprinkles!!!!
a little tip.... not exactly about what you are asking but here goes anyway...
Most of the neoprene collars and plugs you buy will deform themselves after ... lets say...3 months... plus.. they are not the cheapiest to buy. if you own a drill.... do the following (this is assuming you are in the usa) go to your local lowes, home depot or (prefferably) harbor freight store. (also harborfreight.com)
get a hole saw kit. get a drill if you dont have one... and then either again go to, or order from harbor freight their neoprene floor mats. You get 4 large pieces of floor matts for approx 5-7 dollars. You can EASILY drill/cut out 100+ plugs from each piece. It will take a little time but in my opinion... putting your name out there less for growing supplies is reducing your risk for ever getting popped. I have used these same plugs for over 6months now and they still look brand new. I will NEVER buy plugs or collars again. Also, you can cut them to any size you want so if your set up changes... no need to buy more. Just cut them to a different size.
Almost forgot to mention... Take a razor blade, xacto knife, box cutter etc and cut a slit in the center of the newly cut plug. Cut it from the middle out to the edge of the plug. (make it look like a pacman) This way the slit pinches together and holds the plant right where you want it when you put it in the unit. I never had one slip or drop down.
Hope this helps you save some money.
Cheers