CeramicSpeed OSPW Alloy SRAM eTap Pulley Wheel - Alternative BlackSpecifications The overall power savings of the OSPW System for SRAM eTap reach 40% 60%, or more in some cases, over a stock setup. The oversized pulley wheels have 3 5 times longer lifetime than the commonly used standard pulleys on the market. The OSPW system for SRAM eTap derailluers is compatible up to a 32 tooth cassette size and with both short cage & WiFli derailluer bodies. The product is for 11 speed eTap and is not compatible with 12 speed