Excellent product, simple install and programming. I’ve ordered twice. First time for a one transmitter, two receiver kit. Transmitter for the front door, a receiver each for upstairs and walk out lower level. Later decided it would be good to have a transmitter at the downstairs door, too. Asked Monoprice support about adding to an existing kit like this. They responded they had no technical information available. I came back to them and asked if they had a web address for AuYOU or other contact point. They said no. Really? I asked how they ordered more if they wanted to, or did they just wait for AuYOU to contact them? They didn’t answer that one. I decided to risk $9.99 and ordered a two transmitter, one receiver set. I only needed the one transmitter and it works perfectly with the other set. Be near one of the existing receivers, press the programming button and press the button on the new transmitter. Done! And now I have a spare transmitter and a spare receiver to boot. BTW: All the tech specifications are ON the Monoprice page for this item. I’ve ordered a LOT from Monoprice and have never been disappointed in their products. They’ve all been as advertised and usually more than I expected. Only my interaction with their support staff has been disappointing.