I purchased the 8.0GB (2x 4GB) PC3-12800 DDR3L 1600MHz SO-DIMM 204 Pin CL11 Memory Upgrade Kit for my 13" summer of 2015 Non-Retina display MacBook Pro (MacBookPro9,2)
The memory arrived in about two days via USPS with free shipping. (I should add that I live within 30 miles of OWC in Northern Illinois.)
The back of the non-retina MacBook Pro is secured by 10 #00 Phillips screws. Three of the screws are long (about 6-7 mm if I remember correctly) and are easily distinguishable from the seven shorter screws (about 3-4 mm). However, the shorter screws consist of two sets of 3 and 4 screws, which have the same length but have different head shapes. Close inspection of the heads of the shorter screws will distinguish the difference. Be sure to keep the two sets of shorter screws separate.
I used a pill box (with compartments marked S,M,T,...,F,S) to store the screws after removal. A magnetized screwdriver also helps.
I also used used two "spudger" tools (yes, that's how they are spelled in any computer tool catalog) to lift the battery terminal from its socket and to help seat the replacement memory. The two spudgers are not absolutely necessary, but they do help.
The original 2 x 2GB memory chips are held in a spring loaded clip. When the springs are pushed aside (with thumbs or spudgers), the clip springs up 45 deg and the chips are easily removed. The replacement memory can then be slid into place and thoroughly seated using the two spudgers to simultaneously push each end of the chips. The terminal is then pushed back down to the board.
I had no trouble seating the two 4GM chips from OWC into place. They seem to be the exact same size of the original chips, although they do look different.
The whole process took me about one-half hour, but I work slowly and wanted to poke around to see what could be easily replaced in the computer. (The HDD, DVD, and battery are serviceable, although only with a specialized screwdriver.)
The job could easily be done in ten minutes if time were important. It was an easy job and went smoothly. I am thoroughly pleased with the OWC memory set.