There are two definitions for the term shelf bra. The first refers to a thick elastic band that supports under the breasts but does not cover the nipple. This type of bra may be used in lingerie sets. More commonly we see the term shelf bra used to describe a variety of built in bras in garments where wearing a bra would be difficult because of thin straps.
The shelf bra of the first type is connected to eroticism and is not popular wear for all women. Since only minimal support is given, they may be particularly unflattering to women with larger busts, since only a tiny amount of cup or sometimes no cup actually supports the breasts. They may thus be inadequate to providing the support needed for daily wear. Women who would still like to reveal some cleavage might look to the demi-bra, which provides a greater amount of cup support, with cups stopping just above the nipple.
For the second definition, you will see this type featured in a variety of garments. One of the most common uses today is in tank tops. The shelf bra has long been a feature of swimsuits for women who either want extra support or who would like to add a bit more feminine curve to their suits.
The simplest type of bra simply has elasticized cups made of soft fabrics like cotton or nylon. Some may feature a small amount of padding for additional support. Another type -- quite common in tank tops and swimsuits -- is the molded cup style.
The molded cup bra has a semi-hardened shape, which it retains even when you are not wearing the garment. The trouble is, women who wear similar sizes may not all have the same breast size. A large, medium or small tank top with a molded cup bra will not fit everyone the same way. While usually women with breasts slightly larger than the molded cup can fit into this form of shelf bra, women with smaller breasts may run into some embarrassing issues.
Molded cups are firm, but they are not rigid. Hence, cups can be deflated with a little pressure. This is particularly common when you’re swimming, since enough water pressure can easily dent a cup inward, if the cup is too large. This can necessitate racing back to the changing room or a private area to push the cup back out. It’s recommended you avoid the molded cup unless you can find one that fits well.
Occasionally, especially with the popularity of tight-fitting, spaghetti strap tank tops and camisoles, you may find these with a shelf bra in lingerie departments. These are sized according to cup size rather than by women’s clothing sizes. Again, most still depend upon women of certain cup sizes fitting into certain clothing sizes. Yet you are more likely to find a well-fitting tank top with a shelf bra in the lingerie department, than to find one in a standard ladies’ clothing department or store.