Having just changed my car from an 05 Vauxhall Signum which had factory fitted reverse park sensors to an 07 Vauxhall Signum which didnt have any fitted, I scoured the internet for something which would do a similar job. Eventually I came across these looked at the price and thought mmmmm too good to be true but then having read the 30 odd reviews I thought well they cant all be wrong so decided to take the plunge. I need not have worried, I could have fitted them myself but decided to let my local small garage fit them (not main dealer) as I wasn't sure if the bumper needed to be removed, incidentally we thought it would have to be because of the square beam that sits directly behind the plastic bumper but it didn't need to be removed, if you have a Signum and look at the beam from under the car it does appear to be square but behind the plastic its a sort of concave shape so there's plenty of room for the sensor to fit on the inside. The other reason I got the garage to fit it was because initially I had read on the internet that it would need a single by pass relay unit fitted as the signum has a bulb failure detection system which may cause the parking sensor unit to beep every 30 seconds or so if it was connected directly to the live wire of the reverse park light and it may also cause the warning light on the dash to incorrectly report that the reverse light was not working. I have since contacted a local auto electrical technician who advised me that on the Signum it is quite ok to connect as per the instructions, red wire to the live on the reverse lights and black to a good earth, I relayed the info to my man at the garage and hey presto no faults showing on the dash and no bleep from the RP unit every 30 secs, it does exactly what it says on the box so I am one happy bunny, don't waste your money on other expensive units these do exactly the same job and come in various colours, my mechanic even asked me to let him have the details as he was so impressed with them.