I just took off the bottom bracket on my 2002 Giant Hybrid. I looked at the cartridge, and it says it's 121.5 mm long. But after looking at Nashbar and other common cycling sites I can't find a bottom bracket that long. Is this old and outdated or am I missing something? Any advice on what I can get as a replacement?

Here are two photos for you to see what I'm talking about:

The axle is 121.5 mm long. The bottom bracket is 68 mm wide.
Nashbar lists a 68x122 right now.

Okay, so I imagine it's not a big deal if the axle length is a little bit different then. But I suppose I wouldn't want to go down to 113 or anything like that. Thanks for clearing that up.

It is a big deal because your cranks are made for a specific bottom bracket axle length. If you go out too much, your chain line will be off center.

A half a mm is NOT a big deal.

Maybe not half a mm, or a mm. But you can't ignore the axle length - it makes a difference and it is better to go with the specs. Why bother getting something of a different size if you can buy the correct size quite easily?

Because it's not that easy. First of all, I don't see the 68x122 mm BB on Nashbar previously mentioned (maybe I'm blind). I've searched across the Internet and I think I MAY have finally found a 68x121.5mm BB, but I'm not totally sure (it doesn't look like square spindles...are those just covers on the last item on the following page?):

https://www.bicyclefitness.com/info/intsale.html

Don't worry about it. Half a millimeter won't affect anything.

I read it. I just don't believe it.

BB SEARCH 121.5

Just give your local bike shop a call. They will be able to order one in for you. As DMF said, a very small amount won't make a difference though.

I got lucky today. My not so LBS had exactly the BB spindle I needed... a 3U, 124.5mm.

Of course.

Shimano UN53 68X122 isn't listed as being in stock. My bad. Nashbar/Performance: They don't always have what you need.
Bikeman lists a UN54 68x122. https://www.bikemannetwork.com/biking...QRSHMTN/CR5371