POTTER&BRUMFIELD - TE CONNECTIVITY W28-XQ1A-20 Thermal Circuit Breaker, W28 Series, 250 VAC, 32 VDC, 20 A, 1 Pole, Panel Kopul M5015 black cover caps are that

black cover caps are that can be placed over the exposed ends of the bolts

Diameter: 5

This is a ARM Microcontroller

the bottom verticle spacer piece is removeable to reveal a 1/4"-20 male screw

POTTER&BRUMFIELD - TE CONNECTIVITY W28-XQ1A-20 Thermal Circuit Breaker, W28 Series, 250 VAC, 32 VDC, 20 A, 1 Pole, Panel Kopul M5015 black cover caps are thatThe W28 XQ1A 20 is a 20A push to reset fuse holder type Thermal Circuit Breaker, calibration will continuously carry 100% of rating, may trip between 101% and 134% of rating, must trip at 135% in one hour at 25C. Ten times rated current is resettable overload capacity, over 1500V RMS dielectric strength. Snaps into panel from front mounting, 250VAC 32VDC voltage rating. 0. 250 inch quick connect will mount in 0. 032 to 0. 062 inch thick panel.