414b is an r12 alternative. its like the replacement you bought, it doesnt need an oil replacement. it might be similar as the mac-freeze, or freeze12, but its likely that it is not because 414b still affects the ozone layer, just less than r12. so the normal person can not buy it make. i know that you know that you cant mix r12 and 134a so check if the stuff you bought is comapible for r12 systems or did you already use it? does it work? and this membrane im talking about is like a valve i dont know what kind of material they use but when i changed the system over with 414 it died very quickly. those other products like the leak detector, i think can only be used when the system still works but is not blowing really cold air, unless you fill it with enough gas to get the compressor clutch to engauge. if your a do it your selfer like i am but dont want to ga as far as getting a licence just change all the seals in the a/c system including the compressor shaft seal and take it to an a/c shop and just get the system filled because the system needs to be vacumed first to get all the moisture out/ water in an r12 system can make hydro chloric acid and it will eat the aluminum pipes slowy but surley and not to mention it can cause to your compressor.