Related Clues:

• Shell of tortoise or crustacean
• Hard thick shell of some creatures
• Shell makes your car go at a speed of a tortoise
• So a step by car is not for 28 across
• It's hard to get outside a motor over a speed like this
• It's hard for a tortoise to have speed of 23 down
• Shell is what gives a car a speed that's hard outside
• It's hard to get a vehicle over a certain speed
• Shell gives a motor a speed of a tortoise
• Shell gives a speed to a car
• Motor with a speed a tortoise has when it's outisde
• Shell gives a car a speed - of a tortoise
• Hard thick shell, of a turtle say
• For motoring at a speed for a tortoise
• Means to travel quickly? It's hard