Sizing guide
Measure once. Pick the right size.
RailClamp Base ships in four sizes that match standard stainless marine rail diameters. Two minutes with a caliper or a piece of string is all it takes to know which one fits your boat.
How to measure
Three ways. Same answer.
01
Caliper
Most accurate. Measure across the outer diameter of the rail at any clean spot. Read the number.
02
String
No tools? Wrap a piece of string once around the rail, mark the overlap, then divide that length by 3.14.
03
Coin trick
A 5 ¢ Euro coin is exactly 21.25 mm. If the rail is just thicker than the coin, you need 22 mm. If clearly thicker, 25 mm.
Same body, different cradle
Four cradles. One mounting interface.
The four diameters share the same M5 mounting pattern on top, so any Phone Holder, GoPro Mount or Cable Guide locks into any Base, regardless of which rail size you picked.