Hi, its very difficult to open the original casing for the key. Its welded together.

I have had a new casing for mine and had to open the old one with a hack saw.

Below is a link of what i bought, it was realy good value for money. I went to my local key cutting shop and had the blade cut and then i replaced the transmitter and it works a treat.

BMW 3 BUTTON REMOTE KEY CASE SHELL 1 3 5 6 7 X5 X3 | eBay UK

Cheers,

Roy.