When selecting a Roller Ski, consider the following: Skill Level Terrain Surface Type of training First determine your skiing skills. Some roller skis require very good balance, others are quite stable. Will you be skiing in flat or hilly terrain and is the pavement smooth or rough? You also need to determine if you want a slower ski for a harder workout or a faster ski for an easier workout. If the pavement where you will be skiing is rough or if you want to ski on dirt trails the choice should be one of the V2 Aero models. If you have access to smoother pavement you have a choice of many models. If the terrain is hilly you should choose a model that has good speed reducing ability with the speed control device engaged. The efficiency of the speed control device is listed in the following table. The Aero speed control system is the most effective in hilly terrain.
Model	Wheel width	Wheel diameter	Wheel Base*	Replacement wheels		Speed	ATR Speed Reduction	Stability Rating	Ride Comfort	Skier Ability
	mm	mm	mm	Rear	Front
910	40	70	684	W10	RW9	S	C+	B	B	Strong Elite to Novice
920	40	70	684	W20	RW9	MS	C+	B	B	Strong Elite to Novice
930	40	70	684	W30	RW9	M	C+	B	B	Elite to Novice
910K	40	70	744	W10	RW9	S	C+	B	B	Strong Elite to Novice
920K	40	70	744	W20	RW9	MS	C+	B	B	Strong Elite to Novice
930K	40	70	744	W30	RW9	M	C+	B	B	Elite to Novice
940C	33&40	70	684	W94	W83C	MF	C+	B	C+	Elite to Novice
830	40	70	600	W83	W83	M	C+	C+	C+	Elite to Good
840	40	70	600	W84	W84	MF	N/A	C+	C	Elite to Good
840R	33&40	70	600	W84	W83	MF	C+	C+	C	Elite to Good
850	33	70	600	W85	W85	MF	C-	C+	C+	Elite to Novice
6400	25	80	605	W80S	W80S	MF	C-	C-	C	Elite to Good
Aero CL	31	148	742	W150	W150C	MF to MS	A	**	A	Elite to Novice
Aero SC	31	148	686	W150	W150C	MF to MS	A	**	A	Elite to Novice
Aero 125RC	25&31	125&148	730	W125SR	W1150C	MF to MS	A	A	A	Elite to Novice
Aero 150S	31	148	604	W150	W150	MF to MS	A	C-	A	Elite to Good
Aero 125SR	25	125	578	W125SR	W125SR	MF to MS	B+	C-	A	Elite to Good
Aero 125SRM	25	125	515	W125SR	W125SR	MF to MS	B+	C-	A	Elite to Good
Nord. 125SR	25&31	125&148	616	W150C	W150C	MF to MS	A	A	A	Elite to Novice
S=Slow, MS=medium slow, M=medium, MF=medium fast. *Wheel Base = Distance from wheel axle to wheel axle, i.e. distance from the center of the front wheel to the center of the rear wheel. For stability, ATR Speed Reduction and Ride Comfort, A=Best, D=Poor. For stability, the Aero two wheel skis are rated lower because the skier must have better technique and stability than for the wider smaller diameter wheels. **For classic, the Aero CL and SC are quite unstable without Outriggers and rated D for stability. With one Outrigger they are rated C, with two Outriggers B. For skating, the SC is rated C+ and when equipped with one Outrigger, B for skating.