1) Two Vein Model This product permits the realistic practice of venipuncture techniques as well as being an excellent model to practice the mechanics of the newer no stick IV catheters. This model displays blue veins which are barely discernible through the semi- transparent, tissue like material. A "pop" is felt as the needle enters the vein. If resistance is experienced, the tip has either not been advanced far enough or advanced too far. This two vein model has two different sized veins positioned at the same depth. Size: 2 7/16"x 5 5/8 "