Original marketing materials for the Mac Pro generally referred to the middle-of-the-line model with 2 × dual-core 2.66 GHz processors. Previously, Apple featured the base model with the words "starting at" or "from" when describing the pricing, but the online US Apple Store listed the "Mac Pro at $2499", the price for the mid-range model. The system could be configured at US$2299, much more comparable with the former base-model dual-core G5 at US$1999, although offering considerably more processing power. Post revision, the default configurations for the Mac Pro includes one quad-core Xeon 3500 at 2.66 GHz or two quad-core Xeon 5500s at 2.26 GHz each. Like its predecessor, the Power Mac G5, the pre-2013 Mac Pro was Apple's only desktop with standard expansion slots for graphics adapters and other expansion cards.