Hi! First post in mtbr so sorry if this is not the right section.

I recently bought an old Felt Redemption 2 - 2008 frame. It came with an external cup FSA headset which doesn't work quite well. Also, since the frame is pretty big and the external cups are quite high, most of the forks I've tried come short on the tube.

So I was thinking of buying a zero-stack headset for it, however, since I don't have the tools to get the cups out, I was going to buy the headset on the internet and have my LBS install them for me.

However, since I can't get the cups out, I can't measure the diameter of the head tube to buy the new headset, and I can't seem to find this measure anywhere on the internet.

Do any of you happen to know the diameter to buy the new headset? I presume it's 49mm (it's an oversize 1.5" tube), but I need to know for sure.

Thank you!