Also known as a through deck fairlead or bush, rope guide and thru-deck bush.
This push in rope guide is elongated and features rope friendly radiused edges.
Designed to be used as a tidy passthrough for ropes which might need to be guided into a cam cleat on the other side of the deck.
To install, cut a hole to match the external diameter of the bush, apply a bonding agent, and then push the bush into the hole. The glue/ bonding agent is required to hold this style of bush in place.
Stainless steel is a hardwearing, economical option.