https://community.usa.canon.com/t5/Speedlite-Flashes/mr14-ex/m-p/94488#M2183 <P>It screws into the filter threads on the end of your lens.&nbsp; The 100mm has a 58mm filter thread size (every lens will have this printed either on the ring on the front element or somewhere on the body usually near the front element.&nbsp; Double check, because there's also a 100mm L series lens by Canon, and it has a 62 or 67 mm filter size.</P><P>&nbsp;</P><P>You need the <SPAN>Canon Macrolite Adapter 58C</SPAN>.</P> Wed, 21 May 2014 14:32:13 GMT Skirball 2014-05-21T14:32:13Z https://community.usa.canon.com/t5/Speedlite-Flashes/mr14-ex/m-p/94468#M2182 <P>Hello all,</P><P>have bought the 100 macro is usm lens and the mr14 ex ring flash. Small problem is I need the adapter to mount the two. Can some one advise on the part number.</P><P>Many thanks</P> Wed, 21 May 2014 12:51:48 GMT https://community.usa.canon.com/t5/Speedlite-Flashes/mr14-ex/m-p/94468#M2182 Jeff53 2014-05-21T12:51:48Z https://community.usa.canon.com/t5/Speedlite-Flashes/mr14-ex/m-p/94488#M2183 <P>It screws into the filter threads on the end of your lens.&nbsp; The 100mm has a 58mm filter thread size (every lens will have this printed either on the ring on the front element or somewhere on the body usually near the front element.&nbsp; Double check, because there's also a 100mm L series lens by Canon, and it has a 62 or 67 mm filter size.</P><P>&nbsp;</P><P>You need the <SPAN>Canon Macrolite Adapter 58C</SPAN>.</P> Wed, 21 May 2014 14:32:13 GMT https://community.usa.canon.com/t5/Speedlite-Flashes/mr14-ex/m-p/94488#M2183 Skirball 2014-05-21T14:32:13Z