There has been a lot of good reviews of the NP3 coating that Robar offered but Robar is now permanently out of business. The NP3 coating technology is owned by Coating Technologies LLC but they have not found a gunsmithing vendor to handle their product yet. I was planing on having one of my pistols done in NP3 but at the moment no one is available to offer this service.
http://coatingtechnologiesllc.com/robar-closure/
http://coatingtechnologiesllc.com/robar-closure/