These Double ended dildo sex toys come in mostly glass, and silicone.  We stay away from those made of vinyl.  Some Double Ended Dildos can be manipulated to curve to the user's specifications such as Dilio, or are already formed for dual penetration with or without the harness.  Tantus makes the Feeldo line and has recently aded a new line called Renaldo for those who prefer the more realistic cock look.  Fun Factory also makes a line called Share with different sizes both non vibrating and vibrating.  Both companies have a pocket to insert a vibrating bullet.  Fun Factory's bullet is rechargeable though.  

For glass Double Ended Dildos, Icicles, makes a wide selection and the Spartacus' Double Ended Dong is very popular due to the ridges at the end.  Cool or Chill for erotic sensation play.

Fun Factory
$89.99
Sonic Dildo for Two The ergonomic and highly flexible shape of Sonic guarantees endless ways to have fun solo or together. This unique double ended dildo is so flexible that it can fold and be inserted vaginally and anally at the same time. One end is...
Icicles
$45.00 $44.00
Icicles #55 Double Ended Dong Pipedream Products Icicle line Icicles #55 glass probe. Elegant, upscale, and hand-crafted with amazing attention to detail, this luxurious line of glass massagers will leave you breathless. Each hand-blown Icicle glass wand...
SI Novelties
$33.36
Man Magnet Double 16 inches realistic looking dildo. Color one end is red and the other end is black. Slightly curved. Smooth with a wrinkled natural look. Always clean before and after use. A water based lubricant is recommended.
Pipedream Products
$62.00
King Cock 16 inches Thick Double Dildo Flesh. Do you want your first dildo to look and feel just like the rock hard stud you have always fantasized about? Stop dreaming and get down with the King! Every vein, every shaft, and every head is carefully...
Pipedream Products
$54.00
King Cock 16 inches Tapered Double Dildo Tan. Do you want your first dildo to look and feel just like the rock hard stud you have always fantasized about? Stop dreaming and get down with the King! Every vein, every shaft, and every head is carefully...
Pipedream Products
$38.00
King Cock 12 inches Slim Double Dildo Tan. Do you want your first dildo to look and feel just like the rock hard stud you have always fantasized about? Stop dreaming and get down with the King! Every vein, every shaft, and every head is carefully...
Pipedream Products
$34.00
King Cock U Shaped Double Trouble Medium Tan. Do you want your first dildo to look and feel just like the rock hard stud you have always fantasized about? Stop dreaming and get down with the King! Every vein, every shaft, and every head is carefully...