F5 MFG

If you want to use the F5 MFG 50rd Glock drum in your Glock 19, then you will need to purchase this tower as their drum ships from F5 MFG as an AR9 model GLK drum.  Its design is to keep a low profile in the PCC AR, so it's a shorter tower than the 19/17, hence the reason this tower is needed if you want to use the drum in your G19.