I have just exchanged an empty Calor 4.5 butane for a FloGas 4.5 butane, it is only slightly taller so fits in the gas locked of our D34P. They do two shapes, the other is not as tall but wider. The locker was designed for Camping Gaz but it was about 3 times the cost of Calor and I am a stingy Scotsman:-) . It was free to exchange the bottle and the refill was about £22 and about £10 for a new type regulator. When I exchange my spare bottle I will need to pay about £35 deposit since the free exchange was time limited.