You can find the Magpul PMAG D-60 5.56mm 60 Round Magazine here.

The Magpul PMAG D-60 is a lightweight, durable and highly reliable 60-round 5.56mm polymer drum magazine for AR-15/M4 and compatible weapons. The unique drum configuration keeps the magazine from hanging down too much allowing for prone firing and easier storage. Features an easy-to-use loading lever, paint pen dot matrix for easy marking, and a rear window for instant capacity indication. Made in U.S.A.

Features:

• Impact and crush resistant polymer construction
• Wide compatibility with most 'STANAG 4179' platforms suchas the AR15, M4, M16, SCAR MK16/16S, HK416, MR556, M27 IAR, IWI Tavor,and others
• Will seat fully loaded on a closed bolt and the bolt hold open feature to lock the bolt back on the last round
• Ratcheting Loading Lever to take tension off the spring for easy loading by hand
• Feed Tower compatible with most loading devices
• Designed to be left loaded for long term storage without any loss of function or degradation
• All components used are corrosion resistant
• Easy to disassemble for cleaning with only a flat-bladed screwdriver or similar
• Anti-glare translucent window on rear of drum allows for easy determination of rounds remaining
• Paint pen dot matrix panel on back of body to allow for identification marking
• Slip-on, semi-rigid Dust Cover prevents grit and debris intrusion during storage and transport

Specifications:

• Weight, w/Dust Cover: 20.5 oz.
• Weight, loaded (M855 NATO): 46 oz.
• Length, max: 7.4 in.
• Width, max: 4.1 in.