Cessna introduced a retractable landing gear version of the 172 in 1980 and named it the Cutlass 172RG. The Cutlass featured a variable-pitch, constant-speed propeller and a more powerful Lycoming O-360-F1A6 engine of . The 172RG sold for about US$19,000 more than the standard 172 of the same year and produced an optimal cruise speed of 140 knots (260 km/h), compared to for the contemporary version. The 172RG did not find wide acceptance in the personal aircraft market because of higher initial and operating costs accompanied by mediocre cruising speed, but was adopted by many flight schools since it met the specific requirements for "complex aircraft" experience necessary to obtain a Commercial Pilot certificate (the role for which it was intended), at relatively low cost. Between 1980 and 1984 1,177 RGs were built, with a small number following before production ceased in 1985. While numbered and marketed as a 172, the 172RG was actually certified on the Cessna 175 type certificate. The FR172 Reims Rocket was produced by Reims Aviation in France from the late 1960s to the mid-1970s. It was powered by a Rolls-Royce built, fuel-injected, Continental IO-360-H(B) engine with a constant-speed propeller. Variants included the FR172E until FR172J. The Reims Rocket led to Cessna producing the R172K Hawk XP, a model available from 1977 to 1981 from both Wichita and Reims. This configuration featured a fuel-injected, Continental IO-360K (later IO-360KB) derated to with a two-bladed, constant-speed propeller. The Hawk XP was capable of a cruise speed. Owners claimed that the increased performance of the "XP" didn't compensate for its increased purchase price and the higher operating costs associated with the larger engine. The aircraft was well accepted for use on floats, however, as the standard 172 is not a strong floatplane, even with only two people on board, while the XP's extra power improves water takeoff performance dramatically. While numbered and marketed as 172s, the R172J and R172K models are actually certified on the Cessna 175 type certificate. Model introduced in July 2014 for 2015 customer deliveries, powered by a Continental CD-155 diesel engine installed by the factory under a supplemental type certificate. Initial retail price in 2014 was $435,000. The model has a top speed of and burns per hour less fuel than the standard 172.