Mas mabuti kung alamin mo muna specs nung dalawang RAM (installed at yung ilalagay pa lang). Gagana yan kung pareho silang ddr3/ddr4 at kung magkaiba man o hindi yung mhz frequency (but still depends if supported ng motherboard). Kung sakali man na magkaiba sila ng frequency, gagamiting speed frequency ng PC mo eh kung alin yung mas mababa, example installed ram mo is 2666mhz then yung ilalagay mo eh 2400mhz or lower then yung mas mababa ang masusunod na frequency which is not really a big deal naman kasi atleast 16GB na ram mo pero sayang pa din yung speed na mawawala.