Check the listing for details. 6pcs Archery 4.2mm LED Lighted Arrow Nock Actomatically for Compound Bow Hunting. Color: Red, Condition: New other (see details). Listed at 24.41 USD. Diameter:4.2mm color:red,yellow,green,blue,colorful Package:6pcs usage:shooting,hunting Description: Fits for compound bow and recurve bow bolt size 4.2mm ID. Attention: if the nock can't lighted up by the pressure of string, please try to push the switch on the nock; High visibility - maximum light transmission, easy to find your arrow even at night or dawn; NO ASSEMBLY REQUIRED, there is switch on the nock, this nock is string-activated type nock, it can be lighted by the pressure of string, if you want the light on before shooting, just push the switch down, if you want the light off, then push the switch up, very easy and convenient. The LED nocks suitable for ID4.2mm carbon shafts. After setting up the arrow, fire the switch at the moment of the string shooting out, and au.