As said above
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,there are differences between rev 1 and rev 2/3
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,however they also differ depending on when in the year the car was made
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,
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so you could have a rev 1 with a rev2 type column
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(ive come across this a few times)
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theres also different lengths of boss
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,so it depends on make as well
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.and what you want
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Remove your wheel
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,and if the horn connection is a flat brass ring
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,you need rev1, if the horn connection has a sticky out plastic bit
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,you need a rev2