Periscope/snorkel kits

I've just bought one of these from Cornwall Model Boats, a periscope kit, by Robbe...it's a cracking little piece of alloy and brass, fully adjustable in length, and looks quite good on my X craft. And for less than a fiver...can't be bad, can it?

Here's the link : http://www.cornwallmodelboats.co.uk/acatalog/robbe-submarine-periscopes.html

There's also a snorkel kit available for the same price.