Natori Racerback Pullover Bra in a Size M in Black, New Without Tags, Purchased at Nordstrom. 

Natori Maternity offers comfortable support, feminine beauty and effortless function. Wireless nursing bra with a slim racerback for versatile coverage and comfort, perfect for pregnancy and beyond.

Size M

Wireless nursing bra for exceptional comfort
Nursing friendly surplice cups are molded for easy access
 Elastic is encased between fabric at the neckline for containment
Signature Bliss Perfection fabric and lace trim gives a luxurious look and feel
Plush, flat elastics offer all day comfort that won't dig into your fluctuating shape