When Zefal was redesigning their pump, we needed to find a viable alternative. What we found is this pump, by Topeak. Topeak is known in the cycling industry for their innovative design and meticulous engineering.

If you have a Zefal pump, or are familiar with them, then you'll be pleased with the Topeak. It has a curved pump head, to allow for seating in the crook of the top tube and seat tube. The head has a valve clamp, to hold the pump in place while you pump. Probably the only major difference between the Topeak and the Zefal is the pump body: While both are made of aluminum, the Zefal is black, and the Topeak is unadorned aluminum.

Sizing:

The pumps are sized according to the space between the tubes.

Small - For gaps 37 - 42.5 cm
Medium - For gaps 42 - 47.5 cm
Large -  For gaps 47 - 52 cm
XL - For gaps 52.5 - 57.5 cm

Or for these frame sizes,

Small - 43-49cm
Medium - 49 - 54cm
Large - 54 - 59cm
XL - 59 - 64cm