Exact replacement for the original Murray GFCI Switch I installed 20 years ago in 1999. for my spa equipment. I only replaced the original 1999 RCD because someone told me the earlier ones were obsolete and were redesigned in 2006 for safety reasons. That's reason enough for me to replace the original! about 5 minutes to take out the old one and replace it with the new one. Hire an electrician to install if you don't have the skills to do the installation yourself -a, phase-b, copper-aluminum connection, etc. let the professionals do it!