From page 53 of the 2004 Music Direct catalog that came today:
E3c Sound Isolating Earphones
The E3c features an efficient low mass/high energy driver and the smallest enclosure in the Shure E Series. This is their latest model, and has a smoother, more extended high-frequency response coupled with a compact and lightweight design. The E3c is particularly appropriate for use with custom ear sleeves that can be precisely fitted by a hearing specialist - following your purchase - for the ultimate in fit and comfort. Balanced armature drivers provide powerful, high-performance audio output in an extremely small format. The ultra lightweight construction makes them one of the lightest earphones available anywhere for portable listening applications. they are ideal for sports, exercise, or any activity where headphones or ear buds may come loose. Like the E2c, the E3c ships with a fit kit, so you can insure the best possible fit with your ear. [size=small]$179.99[/size]