We present a comment on the kinematic variable $m_{CT2}$ recently proposed in Amplification of endpoint structure for new particle mass measurement at the LHC. The variable is designed to be applied to models such as R-parity conserving Supersymmetry
(SUSY) when there is pair production of new heavy particles each of which decays to a single massless visible and a massive invisible component. It was proposed in Amplification of endpoint structure for new particle mass measurement at the LHC that a measurement of the peak of the $m_{CT2}$ distribution could be used to precisely constrain the masses of the SUSY particles. We show that when Standard Model backgrounds are included in simulations, the sensitivity of the $m_{CT2}$ variable to the SUSY particle masses is more seriously impacted for $m_{CT2}$ than for other previously proposed variables.
