I love these headphones.

I ride my bike all over. I wear beanies a lot and needed earbuds that I could wear underneath. I jog and just like to be moving around. So I was looking for something that fit securely and was also resilient to sweat and outdoor use.

My previous experience with earbuds was nothing but frustrating. They shift in the ear, they fall out, they rattle. After I figured out how to place the twist-to-fit earbuds in I was so pleased and amazed at the snug fit that I began bounding around my apartment up and down the stairs, headbanging... and the earbuds didn't shift one bit!

Because these headphones have the standard earbud containing the speaker plus an additional plastic disc-pad that is meant to secure itself in your outer ear, it takes a little time and care to figure out how to wear them comfortably. But within a week of using the headphones, placing them in my ear and twisting them into position was second nature.

It's important to note that for the first couple days when I was getting used to putting them in, they were sometimes uncomfortable or even painful. And my left ear seemed to fit the outer ear disc-pad better. But give it some time. The plastic disc-pads that fit your outer ear are removable and Sennheiser includes 3 different sizes with the headphones.

I bought the Sennheiser headphones before any reviews had been posted, gambling that they'd meet my needs - and coincidently - my needs match precisely what I've described in "Pros."

*note* The headphones haven't been tested TOO hard on the water/sweat-proof claim. But from my experience thus far and from inspecting the materials used I'm confident they'll meet Sennheiser's claims.

In looking for headphones that would fit securely, the only other real options I found were from companies that would actually construct an earbud based on a molding of your ear canal. They were extraordinarily expensive. I got the Sennheiser MX75 for $45 - this unique headphone has been worth every penny.

*UPDATE - 10/3/2006*
1. The weather has finally been cool enough again to wear beanies. And it's not good! My snug fitting beanies put pressure on the part of the earbud that points away from the head - transferring that pressure to the disc that's in my ear - creating discomfort. Dang!

2. I've done quite a bit of working out and sweating with these things with no sign of wear.

3. It's hard to keep the cords from tangling while stored.

*UPDATE - 8/15/2007*
1. Lost the plastic shirt clip used to keep the headphone wires from slipping and sliding around. I used Sennheiser's website to request a replacement since the part was not available from their online store. Within a week I received an email requesting my address so that the part could be sent. 4 months later, I still haven't received the part. For a couple months after I was told the part would be sent to me, I followed up by writing the same employee who'd promised the part. I never received a response. It was very frustrating and I got the feeling my emails were not being received (perhaps an errant spam filter).

2. After about 14 months of use, the right headphone speaker stopped working. It was a little staticky at first and then silent. I used Sennheiser USA's website to start the return process and was quickly given a return authorization(RA) number and an address to return my headphones too. I received a brand new set of headphones (and all accessories including another clip :) in about one week. Good service this time!