The Winged "C" (SED) 6P1P-EB / 6P1P-EV tube (6П1П) is an upgrade for the Chinese 6P1 tube found in a lot of Chinese "hifi" amplifiers.
Some Mono Price amps are using the 6P1P tube while other amps they make use 6P15 (SV83) tubes. These are not compatible with one another. Be sure to order the correct tube. It is best to check what your amp is using currently rather than trusting the manual as we've discovered some of the Monoprice manuals are incorrect.
Note: There is often mis-information provided by Chinese amp sellers that these are equivalent to western 6AQ5/EL90 tubes. Although they share some electrical similarities, these tubes are absolutely not compatible in anyway.