Here's what other sites are saying:
The Janus Pro Large Double Pulley is strikingly similar to Camp USA's popular Janus pulley, with the exception to the sealed ball bearings that ensure efficiency at higher speeds. Apart from that, it has the same features like the main attachment hole that accommodates three carabiners, or the two secondary side holes for proper positioning.
C.A.M.P. Big Wall & Protection Janus Pro Large Double Pulley 2161. A.M.P.'s Janus Pro is a high-strength multi-functional double pulley with large sheaves for high efficiency haul systems. It uses the same design as the Janus with a main attachment hole that accommodates three carabiners two secondary holes on the sides for positioning and a large lower becket hole but features sealed ball bearings for higher efficiency and intensive use at higher speeds. Prusik knots can be installed on either side (aramid cord suggested).
The C.A.M.P. USA Janus Pro Large Pulley is a high-strength, multifunctional pulley for block-and-tackle systems, complex operations and rigging and rescue situations where lots of hauling is involved.
Features of the Camp USA Janus Pro Double Pulley High strength Multifunctional double pulley Sealed ball bearings for High efficiency (97%) Aluminum alloy body and large sheaves Stainless steel axle Prusik-minding