The flextight bracket fits any seat post or seat stay between 18 and 34mm diameter no tools are required to fit a flex tight bracket simply turn the knurled wheel to tighten or loosen its zip tie fits the following cat eye rear lights tl ld100 tl ld110 tl ld120 tl ld130 tl ld150 tl ld270 tl ld 600 andtl ld 610