The Antipiton is essentially a reverse-tapered Z–ton.

Ed Leeper's idea was to stack the Antipiton against another piton to comply with the evolving (and now discarded) clean climbing ethic that was trying to gain traction at the time. The Antipiton did not work very well. The Antipiton would often slide against the other piton rather than hod securely. Setting the Antipiton with a hammer tap would increase its security, but this violated the clean-climbing ethic.

Leeper's Antipiton came in two sizes.

↑ 108: Leeper Antipiton; Regular

• Made in USA [1975].
• Size: 12 mm.
• Weight: 90 g.
• Made from heat–treated 4130 chromium–molybdenum steel.
• Stamped "LEEPER" on the bottom of the of the central web.