SynaptoRed™ C1 is similar to the widely used red fluorescent nerve terminal dye SynaptoRed™ C2 (also called FM4-64) except that the lipophilic tail of SynaptoRed™ C1 is one carbon shorter than that of the SynaptoRed™ C2. Thus, SynaptoRed™ C1 is expected to have a faster off-rate compared to SynaptoRed™ C2.