It's IWB... I agree with what you say to an extent, but Glock & TruGlo TFO sights are pretty common. If they know my glock will fit, and they have the specs for their own holster, and since TruGlo TFO specs are readily available; they should be able to let me know, yes or no, if it will work. If they could furnish me with exact clearance, I could easily figure it out. That's ok, though... I am leaning more toward Desantis or Crossbreed... and may still consider another brand if there is an IWB that supports a 19 with a TLR-1... though I mainly only attach the TRL-1 when I go to sleep... Don't know if I'd want to carry it all the time. Seems like a bad idea.