GT Avalanche seat post diameter

[Swede]

I've recently picked up what I think is a '98 GT Avalanche but it's in serious need of attention & some parts. Can you guys tell me what size seat post it would need? My caliper is measuring the seat tube ID at 26.3mm but I'd like some help guidance.

It's not in a great position for a photo but the frame is like this;

 

[Swede]

I've done what I can with the refresh but I now need a seatpost and saddle to finish. I dropped in a spare 26.8mm seatpost but it rattles around, so I'm guessing I need a 27.0mm?

 

[Salter80]

Hi my Avalanche takes a 27.2mm seat post

 

[Swede]

Thanks, I took a gamble and bought one on eBay and it worked out just fine.