This is a small daughter board that fits into the socket of the "Sally" custom CPU in the Atari 800XL, 65XE and 130XE microcomputers (the RF shield must be removed, otherwise the daugher board won't fit inside). It replaces that CPU with a CMOS, modern, low-power, fully static, currently in production W65C02S CPU and some auxiliary logic.

The package contains the auxiliary logic chips, the capacitors, the resistances, 40 pin strip and the 4 layer board. Suitable W65C02S CPU is not included, you must search for one these, as recommendation, from trusted distributors.