saw this in the arcadia's blog today http://ameblo.jp/arcadiaac/entry-11822285942.html
google translate it :
'Elo you are. It is Mr. K of the membrane in the mechanism responsible representative. Now I'd like to let me found in the blog in a hurry, Query In order to fix the fast pack of "YF-19", The left and right of the parts you want to give the calves do not know! It is not specified in the instruction manual! · · · I have received opinions and. Left and right parts, but I certainly exists, It does not describe the left and right in the manual .... The Do not let there be an explanation to take this opportunity! First of all, please look at the pictures. It is a part of gray in a photograph. As indicated by the yellow arrow, a person who, pointed Please attach it so that the inside of the leg. Have caused trouble, Thank you hasten! !
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i think its about the fast pack