Summary: There are basically two types of wig cap constructions that are the most popular.
1) The most common is the “Wefted Cap.” The vast majority are also known as "capless" wigs. They are constructed from rows of wefts (fringes) of synthetic fiber or human hair that have been sewn together into the shape of a cap, but do not have an underlying solid cap, per se. The more expensive wefted wigs feature a lace inset at the crown which allows the wearer to part the wig and brush the strands in any direction.
A "thin wefted" wig will usually have the rows of wefts spaced farther apart, which makes the wig lighter and more "breathable." A thin wefted wig will often lack the lace inset at the crown. The downside of this is that sometimes the underlying wefting can be seen when the wig is parted on top. An extreme example of thin wefting is a costume wig which can have wefts spaced very far apart, sometimes to the point that the wearer's own hair will show through.
Although becoming less and less popular, some wefted wigs still feature "crimp wefting" or "perma-tease" at the crown. This is the "fuzzy" looking hair that sometimes sticks up at the top of a wig. It is designed to make the wig look fuller (which is RARELY necessary unless you like the "big hair" look). This matt of short, frizzy hairs will also tend to hide the underlying cap construction, which is seen by wig manufacturers as a good thing.
In extremely cheap wigs, as well as many costume wigs, there will be a heavy net cap showing when the wig is turned inside out. These are still classified as “wefted” wigs, but are NOT considered “capless” wigs. This netting is considered to be an outdated form of cap construction, and is rarely seen in a fashion wig made within the last ten years.
All wigs will have adjustment straps at the nape (back neck area) to allow the wig to be sized down for a more snug fit. Generally, these straps will have Velcro attachments, but will sometimes feature hooks that fit into tiny adjustment pockets. Either system works well, and both are used on inexpensive as well as expensive wigs.
2) The second most common cap construction is the “Monofilament-Top.” This is a wefted wig that features an inset of transparent micro-mesh sewn in at the crown, with the individual strands of synthetic fiber or human hair hand-tied into the mesh. Mono-top wigs are generally more natural-looking, as the hair appears to be growing out of a real scalp, and there is no "crimp wefting" to make the wig look artificially full.
This type of cap was first developed for women who had experienced significant hair loss due to chemotherapy, alopecia, or other medical reasons, as the transparent mesh allowed the bare scalp to show through. You may sometimes see mono-top wigs referred to as "medical wigs" for this reason. However, many women with full heads of hair prefer the mono-top wigs for their superior natural appearance. With a mono-top wig, the hair can be more sharply parted on either side of the head than with a conventional wefted cap wig.
There are two notable variations to the standard mono-top wig: one can be seen in the Amore line, which features a double layer of monofilament mesh at the crown. This extra layer protects a bare scalp from irritation caused by the tiny, scratchy knots created by hand-tying the strands into the monofilament material. The other is the multi-directional monofilament crown featured in some of the wigs in the Georgie line. The hair on this type of wig will part sharply and lay down in multiple directions with greater ease than most of the other brands. This type of cap construction is considered to be the finest in the world, and wigs featuring it will start at over $1,000.
All mono-top wigs feature "tape tabs" on the inside of the cap, usually in 4 or 5 spots. These tabs are made of a shiny plastic material, and allow the wearer to use double-sided tape to secure the wig to the head, if necessary. Generally, mono-top wigs are recognized as a higher quality wig product, and are more expensive than standard wefted cap wigs. A slightly less expensive alternative is a wig featuring a monofilament part, rather than a full monofilament top. These are wigs that have a thin strip of monofilament mesh sewn in just at the left, right, or center part line. In these cases, the location of the part CANNOT be changed.
3) For those who wish to add fullness to their hair, a "Honeycomb" or "Pull-Through" wig or hairpiece may be the answer. Honeycomb products feature wefts that have been sewn into a honeycomb design, with very large spaces between the wefts for the wearer to pull her own hair up and through. These pieces are a lot cooler to wear in hot weather than a regular wig or hairpiece. Some women select a honeycomb product in a slightly different shade than their own hair, to give a highlighted or frosted effect when their hair is pulled through and blended in. In most cases, these pieces are held on with pressure-sensitive combs (also known as toupee clips), or small combs.
A variation of the pull-through is the “Hair Integration” system available through Look of Love in their Hair b’ Tweenz line. These pieces feature horizontal rows of wefts (either human hair or synthetic) and are available in various widths and lengths. The wearer’s own hair is pulled through the wefts, adding fullness, length, or both. These attach with the same type of combs as used for wiglets.
4) Another type of cap is referred to as a “Skin Top” which is basically a wefted cap with an insert of scalp-colored plastic sewn in at the crown. Individual hairs are inserted into this material to give the appearance of hair growing out of a natural scalp. Some wigs feature a "Skin Part" which is similar to a monofilament part -- the plastic material is sewn in just at the part line to give a more natural appearance. Once again, the location of the part CANNOT be changed with this type of cap construction. An important note: the scalp color may not be suitable for all ethnic groups, as it is extremely light.
5) The “Dermafix” cap is a specialty cap construction available only through Alan Thomas. Dermafix caps feature rows of a special material, mostly used in the medical industry for burn patients. This rubbery type material secures to a bald scalp much more easily than other types of caps do.
6) A “Wiglet” features a smaller wig cap. Wiglets can be used to cover thinning spots on the head, or to add volume or fullness in general. They come in a variety of cap styles and sizes. There are wefted, monofilament-top, and pull-through wiglets. They are made in dimensions generally ranging from 3” x 4” to 5” x 7” with many more combinations. They usually attach by using pressure-sensitive combs (toupee clips) that are sewn into the top and/or sides of the cap. They can also come with a drawstring attachment. The brand “Look of Love” offers the widest variety of wiglets.
7) A “Fall” or “3/4 Cap Wig” is designed to be worn with the wearer’s own hair showing at the front hairline and down the temples to the ears. Most falls utilize conventional wefted caps. They are attached using a half-round comb at the front (bangs area) and another at the back (nape area) for an extremely secure fit. Some falls feature a cloth headband (almost always black) which affords a slight separation between the color of the fall, and the color of the wearer’s own hair, which can be beneficial when these colors don’t match exactly.
8) Probably the least common type of cap construction is the “Hand-tied.” A 100% hand-tied wig usually starts at $500.00 for a synthetic style, and can get into the $1,000’s for human hair versions. This is due to the labor-intensive nature of making the wig. It takes a worker one full day to completely hand-tie a wig, and after this, the wig still needs to be hand cut and styled. The cap of a 100% hand-tied wig is extremely stretchy, very similar to a nylon stocking. To keep costs down, some manufacturers offer wigs that are hand-tied at the front hairline and/or crown only. There are a few wiglets available in hand-tied versions, as well.