I use NC-22 Sony Noise Cancelling earphones with my Ipod Nano, but I have never been able to get a perfect in-ear fit with any of the supplied rubber ear buds. As a consequence the noise cancelling/reduction is good, but not perfect. These little foam tips make an ENORMOUS difference. It's just like having ear plugs in. They are very comfortable and extremely good at shutting out background noise - in fact so much so that I have taken to sometimes switching off the active noise cancelling on the NC22 because it's not needed. Despite the outrageous price, these tips are worth every penny in my opinion.
PS. there is conflicting information on the internet for which earphones these foam tips fit. Very annoying! There is a list on the back of the packet which I have reproduced here for the T-400 series:
altec lansing backbeat classic, plus, pro;
audio-technica ATH-ANC3, -CK1, -CK7, -CK32, -CK52, -CKM50; Auvio 33-266, - 267, -268, -271, -286, -289;
Creative -EP630 and -EP830;
Denon AH- C252, -C351, -C452, -C551, -C700, -C710, -C751, -NC600; Grado GR8;
Jaybird Endorphin Rush, Tiger Eyes;
Kicker EB 71/71M, EB 101/101M, EB 141
Koss KEB24, KEB79
Memorex EB200A, EB300A
Monster Turbine, Turbine PRO
Panasonic RP-HJE300, RP-HC30
Philips SHE 8500, 9500, 9501, 9600, 9700, 9800, SHS 8000
Plantronics Voyager 855;
Radius Atomic Bass;
Sennheiser CX-95, CX-300, CX-400, CX-500, IE-6, IE-7, IE-8, MM-50;
Skullcandy Titan, Full Metal Jacket, INK'D, Smokin' Buds, Riot, Holua, Asym, Striker;
Sony MDR-AS40EX, -EX32, -EX51LP, -EX55LP, -EX71SLA, -EX75, -EX81LP, -EX85LP, -EX90LP, -NC11, -NC22;
Ultimate Ears Metro Fi: 100, 150, 170, 200, 220, SuperFi 4/4vi, SuperFi 5/5vi;
V-Moda Vibe, Vibe II, Vibe-Duo, bass-freq, sport series;
2XL Bunny, nuevo sonido, snake eyes, wrecking ball.
I can't vouch for how accurate this list is, but this is copied straight off the back of the pack. More details are on the comply website.
By the way, I ordered from Handheld Audio and they came within two days. Very good service.