Some people like to wear a tallit katan with extra long tzitzit strings. Here's an inquiry that came in today:

Hello,

I'd like to order three sets of white, cotton tzitzis, size 24in, tied Chabad, but with strings that are thicker and longer than the commonly sold chabad tzitzis. I seem to remember reading that you can tie custom tzisis. Are you able to do this? If yes, please let me know how much the total is and how I can pay.

Thank you,    Victor S.

I never know for sure what people mean when they tell me they want to buy extra long tzitzit, because that could mean 60 cm for thin or 70 cm or 80 cm for thick. I explained to Victor that typically tzitzit on a tallis katan are standard length thin, which are 50 cm and on a tallis gadol standard length thick, which are 60 cm. 

My guess is that he wants the regular thick, which is listed among the options right on the product page (here).

Some people want them even longer than 60 cm (often yeshiva bochurs want really long strings). If that's what you're looking for you would do this:

1. Choose a tallis katan
2. Choose the "I don't need tzitzis" option
3. Choose the tzitzit tying option (Chabad?)
4. Add to cart
5. Go to this page
6. Add to cart