The filter thread size of Tamron 18-300mm F3.5-6.3 Di III-A VC VXD is 67mm.
Below are links to the filters that we recommend you to consider for your Tamron 18-300mm F3.5-6.3 Di III-A:
Read our detailed Tamron 18-300mm F3.5-6.3 Di III-A VC VXD Review