It is a common fallacy that vibrators are only for women.  Even though men usually do not have the same difficulty in achieving orgasm that women often do, a vibrator can provide great stimulation on the head, shaft and base of the penis, as well as the testicles and anus can all be stimulated enjoyably. Some men find that the vibrator is great to massage the area underneath the scrotum as they give themselves manual stimulation. This can produce a fantastic orgasm.  Vibrators can even help some men that can't get an erection to have an orgasm. There are vibrators that are made exclusively for men which include vibrating sleeves and vibrating penis rings.  Anal vibrators can be enjoyed by both men and women.   With the exception of the clitoral strap-on women's vibrator, most of the various vibrators can be used for male stimulation and sexual enhancement.

Vibrating Sleeves - sleeves were designed specifically to enhance masturbation. They come in a variety of materials, shapes and colors.  The penis is inserted into the sleeve and the man can have the choice of either thrusting or allowing the vibrator to do all the work.  Sleeves manufactured from Cyberskin or Jelly have the most realistic feel.  Of course, sleeves are also constructed in the non-vibrating version too. Vibrator sleeves can also be molded from a woman's genitals and these usually have a vibrating bullet located in the center of the Vagina or Anus.
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Vibrating Pumps - pumps were designed to help pull blood into the penis thereby creating both an erection and making the penis temporarily thicker.  Pumps are now on the market that vibrate at the same time they are creating a vacuum. 
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Vibrating Cock Rings - create a stronger and longer lasting erection plus greatly enhance intercourse for both parties.  Most are rubber or jelly with a bullet vibrator attached at one or both ends. 
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Anal Vibrators -  Anal vibrators can stimulate the anal opening, the prostrate and the rectum. The anus is a very sensitive area and most important thing is to use plenty of lubricant as the anus has no natural lubrication. Start by just touching and stroking the outside of the anus. When you feel you are ready, insert the vibrator, moving it in and out slowly. Remember to use a condom on any anal vibrator if it is going to be shared with a partner. 
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Summary 
Vibrators can be a great enhancement to masturbation.  They can be used to stimulate every part of the male body.  Experiment with running a vibrator up and down the shaft of your penis. Hold it against and between your testicles. By applying a vibrator to the perineum, you will be externally stimulating the prostate.  Women's G-Spot vibrators can also be used to stimulate the prostrate.  Try different positions and different levels of pressure and different vibrator speeds to find your maximum pleasure quotient. Always use a lubricant to prevent irritation to the genitals.  There are special lubricants designed for masturbation.
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Remember to clean your vibrator after every use and always clean before sharing it with a partner. 
(Read more about Care and Cleaning Your Vibrators Here!)

Also See:
Vibrator Instructions For Women
Vibrator Instructions For Couples