Buy these. Hands-down: they're the best Glock guide rods on the market:
- They fit my Gen4 perfectly and work with ISMI and Wolff springs, so you can load whatever spring strength/poundage you want without having to use any awkward/annoying washer/adapter
- They're reliable - I've shot 100,000 rounds through mine, and it's still working great
- These are polymer, so, they're legal for every division in IDPA and USPSA
- Billy is a great guy and awesome to work with

I've bought around six of these for friends, and they've also been very happy with these polymer guide rods.