The numbering for these ascenders may seem confusing - it is. The best explanation that I can offer is that the A1-811 was probably not numbered correctly when I bought mine (1994), and should have been the A4-811.
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The A4 816 is designed to be a chest ascender for the Frog System. The body is milled from an aluminum extrusion that sets the attachment holes 45 degrees to the plane of the cam motion. This works, but leaves a ridge that sometimes digs into the chest. I find that the Kong-Bonaiti Cam-Clean or the Petzl Croll are somewhat more comfortable. The frame is rugged to the point of overkill, as one expects from an SRT ascender.
The cam is well made and the teeth are nicely formed. The safety doubles as a hold-open catch for the cam.
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The A1-811 is the "Explorer" series Version of the A4-816. There are minor differences in how the frame is milled, bet these make no functional difference that I can see. The cam is slightly different, and the cam safety is made out of a heavy stamping with a turned pin attached, while the A4-816 cam is a cut extrusion.
For all intents and purposes, I consider these two ascenders to be interchangeable. Neither has a clear advantage over the other.
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The SRT catalog lists this as the A4-816 R, but the receipt listed it as an A4-816 L. I think that the latter makes more sense, but it doesn't really matter what you call it - its a larger Version of the A1-811 (now called the A4-811 R, or is it L?) that can handle 8 to 16 mm. ropes for the "bigger is better" crowd.
[ Top | A4-816 | A1-811 | A4-816 L ]
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©2007, Gary D. Storrick