This MRB design is probably Mark's most copied invention, invented way back in 1987 and is probably the most copied part ever made for a Lambretta.
Always insist on genuine MRB parts and not copies.
This item is essential in any tuned scooter and we recommend it even in a standard scooter.
This chain slipper evolved because we found that the standard Lambretta top chain slipper wasn't strong enough to do its job in a Lambretta engine and can be quite dangerous when it snaps.
We recommend leaving about 6mm play (total up and down) in your chain.
People sometimes ask for a new piece of nylon for their chain slipper when it has worn down a bit but you do not need it - the rollers of the chain will run on the nylon.
We have never seen a chain wear all the way through the nylon on one of our slippers.
These are also known as chain adjuster or chain tensioner.