These cable glands fit precisely, to the thread, into the circular holes:
uxcell[emoji768] 10 Pcs Black Plastic Waterproof Cable Glands M20 x 1.5 https://www.amazon.com/dp/B007Q846A4/ref=cm_sw_r_cp_awd_jxx9wb78QRVJ5
They fit in the oval holes too with a sliced-in-half-lengthwise rubber grommet from this kit:
125pc Rubber Grommet & Plug Assortment - Includes Solid Plugs - Automotive, Airplane, Marine Applications https://www.amazon.com/dp/B00552Q1P6/ref=cm_sw_r_cp_awd_Syx9wbS3J5CZ6
This smaller gland size works beautifully as well for the circular hole:
10 Pcs PG9 Black Waterproof Cable Gland Connectors https://www.amazon.com/dp/B00BXWVLNE/ref=cm_sw_r_cp_awd_6zx9wb4W5YJ3X
I sealed with this stuff:
3M Marine 5200 Adhesive Sealant, Black, 3 oz https://www.amazon.com/dp/B000Y89JC8/ref=cm_sw_r_cp_awd_VFx9wb91K343V
Here's my install that squeezed 2 16gauge and 2 14gauge wires through the smaller PG9 gland, and 2 10gauge and 4 14gauge wires through the larger.
I think these are quite un-butt, personally.
uxcell[emoji768] 10 Pcs Black Plastic Waterproof Cable Glands M20 x 1.5 https://www.amazon.com/dp/B007Q846A4/ref=cm_sw_r_cp_awd_jxx9wb78QRVJ5
They fit in the oval holes too with a sliced-in-half-lengthwise rubber grommet from this kit:
125pc Rubber Grommet & Plug Assortment - Includes Solid Plugs - Automotive, Airplane, Marine Applications https://www.amazon.com/dp/B00552Q1P6/ref=cm_sw_r_cp_awd_Syx9wbS3J5CZ6
This smaller gland size works beautifully as well for the circular hole:
10 Pcs PG9 Black Waterproof Cable Gland Connectors https://www.amazon.com/dp/B00BXWVLNE/ref=cm_sw_r_cp_awd_6zx9wb4W5YJ3X
I sealed with this stuff:
3M Marine 5200 Adhesive Sealant, Black, 3 oz https://www.amazon.com/dp/B000Y89JC8/ref=cm_sw_r_cp_awd_VFx9wb91K343V
Here's my install that squeezed 2 16gauge and 2 14gauge wires through the smaller PG9 gland, and 2 10gauge and 4 14gauge wires through the larger.




I think these are quite un-butt, personally.