Do like thousands of others, use Rutaseal rubber grommets to seal your cables!
Opposite to common belief many applications do not need IP68 cable glands. Glands are more time consuming to install, often need access from both sides during installation and have very large protrusion.
RUTASEAL is installed from one side only, sealed from the beginning with a push out membrane that is removed by installing the cable. It is self-adjusting to both wall thickness and cable diameter.
Since RUTASEAL is made of EPDM or Chloroprene rubber it is ideal for outdoor use. Compared to plastics, rubber is less likely to dry, crack and come lose, and very resistant to UV-light and ozone. Since the material is soft it is ideal to use on curved surfaces, as it will adapt to the shape of the surface.
Rutaseal is available in different colors, both metric and PG as well as in a Light version. It is SEMKO approved for IP67. The Chloroprene version is also DNV approved for marine and offshore installations.