These tires have a thick section of rubbery substance underneath the tread, and it's thicker than a thumbtack's point is tall, which makes these both weighty and almost flat-proof.  No need for tire liners, no need for Slime, no fear of broken bottles or anything else.  Schwalbe calls this technology "Smart Guard", and it's the best way to go when you're commuting over junk and really, really don't want to get a flat.  

Your choice of either 26" x 1.75" or 700c x 40mm.  Wire bead.

Not sure about which tire to get? Consult our Pick-a-tire chart in this PDF file.