Single Ball Bearing 38mm Block With Becket. This is an upgraded version of the classic Laser mainsheet block used on the rear of the boom for the mainsheet. It features a becket to dead end the mainsheet too. This block is Laser class legal. Manufactured from nylon and features a ball-bearing sheave for reduced friction.Originally designed for the Laser dinghy mainsheet system this classic block has also become the block of choice for many other dinghy mainsheet systems.