Where can I find a good affordable replacement tune for the K40

Lasers
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1

Where can I find a good affordable replacement tune for the K40

2

http://www.ebay.com/itm/New-40W-CO2-Laser-Tube-Water-Cooling-for-the-Laser-Engraver-US-Seller-from-CA-/271812827668?hash=item3f494e9a14:g:8Z0AAOSw9H9U1yTo

3

This is cheaper!
http://www.ebay.com/itm/New-Long-Life-Time-Water-Cooling-CO2-Laser-Engraver-Sealed-Laser-Tube-40W-/141708240324?hash=item20fe7825c4:g:vccAAOSwDNdVlKyi

4

@Joe_Keneally this is the one I was looking at but didn’t know if it was the right size