The filter thread size of Tamron SP AF 11-18mm F4.5-5.6 Di II LD Aspherical IF is 77mm.
Below are links to the filters that we recommend you to consider for your Tamron 11-18mm f4.5-5.6 II LD:
Read our detailed Tamron SP AF 11-18mm F4.5-5.6 Di II LD Aspherical IF Review