Hello! Thanks for checking out this slight variant of the GXL17/34 frames! These use DD17.2 G17 rail inserts, Gen 3 slide, and Gen5 slide lock springs. 

These are deigned to house AR15 buffer weights in a cavity under the slide. The 17 model can fit 3 and the 34 model can fit 4. 
The weights should fit freely inside the cavity but may need to be shimmed depending on many you cram in there, included is a plug which can be inserted and held in place with a 3mm pin.

Much like the non-competition oriented versions I recommend printing with at least 8 walls minimum, 100% infill, using PLA+ or tougher. 
Print it rails down. printing it any other way will get you blocked and reported to the authorities >:(

Questions? Comments? Concerns? Find me on Twatter!