I built my home made lighted knocks tonight. I weighed my other knocks that I have been using, the ones that use the tiny allen screw to tighten them, and they were 16.5 grains. I also weighed the homemade lighted knocks and including the 1/4" x 1/4" tube that I put in the shaft, instead of wooden dowel, and they weigh right at 25 grains. SO a total of 8.5 grains of difference.
This wasa very easy project, and I won't be paying $10 a pop for the factory lighted knocks any more. Very cool little add on to my archery gear!